ci: Migrate to commitizen to bump version

[OliverCullimore]

This should hopefully fix the automated releases.

@robbrad The bump environment will require a Personal Access Token to be passed in via the "PERSONAL_ACCESS_TOKEN" secret with the following configuration if you can set that up before this one's merged:

• Limited to this repository using "Only select repositories"
• "Read and Write" access to "Contents"
• "Read-only" access to "Metadata"

This is to enable the action to update the pyproject.toml and manifest.json files with the new version number without creating a second PR we'd have to accept after each merge.

I've tested this in a copy of the repo so hopefully it'll all just work first time and we can close #329 #346 #347.

Update to also address #326 by using the corresponding tag's version of the file.

[codecov-commenter]

Codecov Report

Merging #348 (2edac7d) into master (e9c151a) will not change coverage.
The diff coverage is n/a.

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

@@           Coverage Diff           @@
##           master     #348   +/-   ##
=======================================
  Coverage   83.44%   83.44%           
=======================================
  Files           3        3           
  Lines         151      151           
=======================================
  Hits          126      126           
  Misses         25       25           

[robbrad]

I think I did it right !