Add `version.json` to match go-cid

[sumanjeet0012]

go-cid has a version.json file. py-cid should have one for consistency across the multiformats ecosystem.

Proposed Solution

1. Create version.json:

   {
     "version": "v0.5.0"
   }

2. Add to bump-my-version config in pyproject.toml.

Related

• Go equivalent: go-cid version.json