Update Actions and Enable Dependabot for GH Actions

[wfondrie]

This PR fixes the current actions and adds support for dependabot.

This also fixes the linting issues in main.

[codecov]

Codecov Report

Attention: Patch coverage is 11.11111% with 8 lines in your changes missing coverage. Please review.

Project coverage is 84.57%. Comparing base (6b8fbfd) to head (eb12c3f).

Files with missing lines	Patch %	Lines
mokapot/parsers/pin_to_tsv.py	0.00%	6 Missing ⚠️
mokapot/mokapot.py	33.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #125      +/-   ##
==========================================
- Coverage   84.60%   84.57%   -0.04%     
==========================================
  Files          26       26              
  Lines        2949     2943       -6     
==========================================
- Hits         2495     2489       -6     
  Misses        454      454              

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[jspaezp]

I think T20 can be disabled in everything under the docs dir ...

[jspaezp]

LGTM, we can fix it later on the files that are making it not pass.
FYI: #126 adds the new actions (except for dependabot)