Misc maintenance - note on changes made

[consideRatio]

WIP, potentially growing list:

• I reduced the default permissions of the github token in the repo, so it doesn't come with read/write permissions by default, but only read permissions. @choldgraf @chrisjsewell this is worth doing org wide and then opt in to permissions.issues=write etc if you need it for some workflow's job.
• @choldgraf your read only PAT is being removed in maint: use pytest-cov, cleanup docs/requirements.txt, and reduce rate limiting issues in CI #169, if merged, let's delete it from this repo's action secrets - agree?