Add .readthedocs.yaml

[natefoo]

This is required as of September. Stolen from bioblend, thanks @nsoranzo :grin:

[natefoo]

I know I didn't cause it but I legitimately cannot find what the actual error is in the test output.

[nsoranzo]

It has been failing for at least 5 months, so...

[mvdbeek]

It's a tool test output that differs, but it's a pain to debug.