Final Steps for Version 5 Release

[x] fix PyPI deployment
- need @jeetsukumaran to verify email address for PyPI account with PyPI
- due to policy change on maintainer reachability https://pypi.org/help/#verified-email
[x] fix ReadTheDocs build (@mmore500)
- rationale: Google is sending users here, so we should probably keep it up to date
- we could take ReadTheDocs down, but we probably benefit from their Search Engine Optimization
- will be completed on https://github.com/jeetsukumaran/DendroPy/pull/195
- [x] need admin access from @jeetsukumaran (add mmore500.login@gmail.com as a maintainer at https://readthedocs.org/dashboard/dendropy/users/create/)
[x] fix Codecov upload in CI (@mmore500 )
- [x] need token from @jeetsukumaran (get "Repository upload token" from https://app.codecov.io/gh/jeetsukumaran/dendropy/settings --- it's ok if the token is posted publicly)
- will be completed on https://github.com/jeetsukumaran/DendroPy/pull/194
[x] review pending proposed changes, as desired/necessary
- PR: expose additional "rerooting" API on Tree: https://github.com/jeetsukumaran/DendroPy/pull/194
- PR: major v5-specific changes https://github.com/jeetsukumaran/DendroPy/pull/176
[x] are there any other must-have features, fixes, or tweaks before release?
- in particular, are there any deprecation warnings we want to change to errors?
- probably worth a scroll through items that are currently deprecated https://github.com/search?q=repo%3Ajeetsukumaran%2FDendroPy%20deprecate&type=code

Once these action items are complete, @mmore500 will use bumpver to tag v5.0.0 on main and then CI will deploy to PyPI. :tada:

jeetsukumaran / DendroPy