ci: Document release workflow, make release manually triggerable

Author: buffcode

.github/workflows/npm-release.md

@@ -0,0 +1,18 @@
+# NPM release
+
+1. Bump version:
+    ```bash
+    yarn version --patch
+    ```
+
+2. Push changes and tags:
+    ```bash
+    git push --follow-tags
+    ```
+   
+3. [Wait for tag pipeline to become green](https://github.com/buffcode/ntp-packet-parser/actions)
+
+4. [Create a new release on GitHub](https://github.com/buffcode/ntp-packet-parser/releases/new)
+    - Choose the tag from step 1/2
+    - Title is `v{version}`
+    - Give some description on what changed

.github/workflows/npm-release.yml

@@ -1,8 +1,9 @@
 name: Node.js Package
 
 on:
+  workflow_dispatch:
   release:
-    types: [created]
+    types: [released]
 
 jobs:
   publish: