Update `CONTRIBUTING.md` with information about version bumping

* SQLAlchemy Easy Soft-Delete version:
* Python version:
* Operating System:

### Description

Describe what you were trying to get done.
Tell us what happened, what went wrong, and what you expected to happen.

### What I Did

```
Paste the command(s) you ran and the output.
If there was a crash, please include the traceback here.
```
