Update docs build

[catanzaromj]

The documentation and build process use outdated github actions. This PR updates these and adds a dependabot to ensure they remain up-to-date moving forward.

There were changes on master that never made it into a release because these procedures were out of date. Therefore, this PR may also fix some other lingering issues as well.

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 80.34%. Comparing base (ece5d47) to head (ec4aaaa).

Files	Patch %	Lines
kmapper/visuals.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #253      +/-   ##
==========================================
+ Coverage   80.32%   80.34%   +0.02%     
==========================================
  Files          11       11              
  Lines         864      865       +1     
  Branches      189      203      +14     
==========================================
+ Hits          694      695       +1     
+ Misses        138      137       -1     
- Partials       32       33       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[catanzaromj]

I had to drop python 3.7 compatibility due to the way sparse matrices/arrays are handled in newer versions of scipy and numpy. Newer versions of numpy (and therefore scikit-learn) raise an error on sparse scipy matrices, in favor of sparse scipy arrays. These were not introduced until scipy 1.8.0, which requires python3.8+.

This arose from me unpnning the dependencies and updating things. Rather than keeping the dependencies pinned, I'm in favor of dropping python3.7 support (its EoL anyways). I think unpinned dependencies is better moving forward so that we stay up to date with the packages we rely on. The built and published wheels can be used for backwards compatibility.