V2 release prep

[BradleySappington]

release preparation for v2.0.0

[BradleySappington]

awaiting feedback from folks looking at the testpypi install:
pip install -i https://test.pypi.org/simple/ --extra-index-url https://pypi.org/simple/ legacy-webbpsf

[marcio-melendez]

I tested the alias on a clean environment and installation. I imported webbpsf and it loaded the alias with the deprecation warning as expected:
DeprecationWarning: "
This message is for information only and WebbPSF will continue to function as normal.
The WebbPSF library has been moved/renamed to STPSF.
Please see https://stpsf.readthedocs.io/en/stable/ for more information.
WebbPSF is now an alias of STPSF and is running code from the STPSF library.

I was able to run webbpsf as expected. The alias uses STPSF_DATA path but if the users set WEBBPSF_DATA then it gets copied to STPSF_DATA .
Overall, a webbpsf user is transparent to STPSF running behind as an alias, i.e., a user can install webbpsf, download the latest webbpsf-data files and run webbpsf with no problems despite the fact that STPSF is the functional code.