modernize GHA `.yml` files merged in #32

[jGaboardi]

Since #32 was initially made there have been improvements, etc. to the GHA. The following should be revisited:

• unittests --> 9f13d2a
• build_docs --> 07e3d79
• release_and_publish (xref release notes debate #35)
• ci/ enviroments --> ac7154b
• setup.py for Python versions --> e061236

[knaaptime]

i think the recipes themselves are generic so they just need to be synced across all subpackages when they're updated in a single place. What about keeping the 'main' recipes here, then including them as submodules in the subpackages, and keeping the submodules up to date with dependabot ?