Fix minor README docs issues in client reference (#316)

## Problem
@haruska pointed out that the headers in the SDK client reference
navigation bar were a little off for "Create Index" showing "Create a
pod index" only. The formatting also felt a bit off with everything
being aligned.

https://sdk.pinecone.io/python/pinecone.html

While fixing this I also noticed the link for the `CONTRIBUTING.md` file
is relative in the README, which doesn't work when linking from our
generated docs.

## Solution
- Promote "Indexes" to a top-level section to visually break up the nav
list a bit, and then swap `Create Index` to the header and moving
`Create a serverless index` and `Create a pod index` to sub-headers of
that.
- Link directly to github for the `CONTRIBUTING.md` file. 

## Type of Change
- [x] Non-code change (docs, etc)

## Test Plan

|Before|After|
| ------------- | ------------- |
|<img width="1166" alt="Screenshot 2024-02-23 at 12 55 08 PM"
src="https://github.com/pinecone-io/pinecone-python-client/assets/119623786/ba6f27b9-4844-4952-9886-7ab820f25196">|<img
width="1170" alt="Screenshot 2024-02-23 at 12 55 32 PM"
src="https://github.com/pinecone-io/pinecone-python-client/assets/119623786/f9ccfe8a-dce4-440a-b1f6-14bb3e78000e">|

You can pull this branch down and build the docs locally. You'll need to
make sure to install the grpc extras with poetry:

```
poetry install --extras "grpc"
poetry run pdoc pinecone '!pinecone.core' '!pinecone.utils' --favicon ./favicon-32x32.png --docformat google -o ./docs
```

This will build the docs in the `/docs` folder under the project folder.
You can open the `index.html` file locally.

Author: austin-denoble

README.md

@@ -1,6 +1,5 @@
 # Pinecone Python Client · ![License](https://img.shields.io/github/license/pinecone-io/pinecone-python-client?color=orange) [![CI](https://github.com/pinecone-io/pinecone-python-client/actions/workflows/merge.yaml/badge.svg)](https://github.com/pinecone-io/pinecone-python-client/actions/workflows/merge.yaml)
 
-
 The official Pinecone Python client.
 
 For more information, see the docs at https://www.pinecone.io/docs/
@@ -10,24 +9,20 @@ For more information, see the docs at https://www.pinecone.io/docs/
 - If you are upgrading from a `2.2.x` version of the client, check out the [**v3 Migration Guide**](https://canyon-quilt-082.notion.site/Pinecone-Python-SDK-v3-0-0-Migration-Guide-056d3897d7634bf7be399676a4757c7b#a21aff70b403416ba352fd30e300bce3).
 - [**Reference Documentation**](https://sdk.pinecone.io/python/index.html)
 
-
 ### Example code
 
 Many of the brief examples shown in this README are using very small vectors to keep the documentation concise, but most real world usage will involve much larger embedding vectors. To see some more realistic examples of how this client can be used, explore some of our many Jupyter notebooks in the [examples](https://github.com/pinecone-io/examples) repository.
 
-
 ## Prerequisites
 
 The Pinecone Python client is compatible with Python 3.8 and greater.
 
-
 ## Installation
 
 There are two flavors of the Pinecone python client. The default client installed from PyPI as `pinecone-client` has a minimal set of dependencies and interacts with Pinecone via HTTP requests.
 
 If you are aiming to maximimize performance, you can install additional gRPC dependencies to access an alternate client implementation that relies on gRPC for data operations. See the guide on [tuning performance](https://docs.pinecone.io/docs/performance-tuning).
 
-
 ### Installing with pip
 
 ```shell
@@ -78,9 +73,9 @@ pc = Pinecone() # This reads the PINECONE_API_KEY env var
 
 #### Using a configuration object
 
-If you prefer to pass configuration in code, for example if you have a complex application that needs to interact with multiple different Pinecone projects, the constructor accepts a keyword argument for `api_key`. 
+If you prefer to pass configuration in code, for example if you have a complex application that needs to interact with multiple different Pinecone projects, the constructor accepts a keyword argument for `api_key`.
 
-If you pass configuration in this way, you can have full control over what name to use for the environment variable, sidestepping any issues that would result 
+If you pass configuration in this way, you can have full control over what name to use for the environment variable, sidestepping any issues that would result
 from two different client instances both needing to read the same `PINECONE_API_KEY` variable that the client implicitly checks for.
 
 Configuration passed with keyword arguments takes precedent over environment variables.
@@ -109,15 +104,15 @@ index.upsert(vectors=[])
 index.query(vector=[...], top_key=10)
 ```
 
-## Indexes
+# Indexes
 
-### Create Index
+## Create Index
 
-#### Create a serverless index
+### Create a serverless index
 
 > [!WARNING]  
 > Serverless indexes are in **public preview** and are available only on AWS in the
->  `us-west-2` region. Check the [current limitations](https://docs.pinecone.io/docs/limits#serverless-index-limitations) and test thoroughly before using it in production.
+> `us-west-2` region. Check the [current limitations](https://docs.pinecone.io/docs/limits#serverless-index-limitations) and test thoroughly before using it in production.
 
 ```python
 from pinecone import Pinecone, ServerlessSpec
@@ -134,7 +129,7 @@ pc.create_index(
 )
 ```
 
-## Create a pod index
+### Create a pod index
 
 The following example creates an index without a metadata
 configuration. By default, Pinecone indexes all metadata.
@@ -144,17 +139,17 @@ from pinecone import Pinecone, PodSpec
 
 pc = Pinecone(api_key='<<PINECONE_API_KEY>>')
 pc.create_index(
-    name="example-index", 
-    dimension=1536, 
-    metric="cosine", 
+    name="example-index",
+    dimension=1536,
+    metric="cosine",
     spec=PodSpec(
-        environment='us-west-2', 
+        environment='us-west-2',
         pod_type='p1.x1'
     )
 )
 ```
 
-Pod indexes support many optional configuration fields. For example, 
+Pod indexes support many optional configuration fields. For example,
 the following example creates an index that only indexes
 the "color" metadata field. Queries against this index
 cannot filter based on any other metadata field.
@@ -172,8 +167,8 @@ pc.create_index(
     "example-index-2",
     dimension=1536,
     spec=PodSpec(
-        environment='us-west-2', 
-        pod_type='p1.x1', 
+        environment='us-west-2',
+        pod_type='p1.x1',
         metadata_config=metadata_config
     )
 )
@@ -242,7 +237,6 @@ index = pc.Index(host=os.environ.get('INDEX_HOST'))
 index_stats_response = index.describe_index_stats()
 ```
 
-
 ## Upsert vectors
 
 The following example upserts vectors to `example-index`.
@@ -356,7 +350,7 @@ from pinecone import Pinecone
 pc = Pinecone(api_key='<<PINECONE_API_KEY>>')
 
 pc.create_collection(
-    name="example-collection", 
+    name="example-collection",
     source="example-index"
 )
 ```
@@ -398,7 +392,6 @@ pc = Pinecone(api_key='<<PINECONE_API_KEY>>')
 pc.delete_collection("example-collection")
 ```
 
-# Contributing 
-
-If you'd like to make a contribution, or get setup locally to develop the Pinecone python client, please see our [contributing guide](./CONTRIBUTING.md)
+# Contributing
 
+If you'd like to make a contribution, or get setup locally to develop the Pinecone python client, please see our [contributing guide](https://github.com/pinecone-io/pinecone-python-client/blob/main/CONTRIBUTING.md)