Suggestion: Clarify the distinction between `tblite` and `xtb-python` in the README

[Andrew-S-Rosen]

As noted here, apparently tblite is the preferred route in terms of using a Python interface to xtb. This, and the overall distinction between when to use xtb-python vs. tblite, should probably be added to the README to help the user out.

[awvwgk]

Whether my personal intent with tblite aligns with the plans for xtb-python is another question. This is a decision which should probably be made by the xtb and xtb-python maintainer teams.

ping Marcel @MtoLStoN, Marcel @marcelmbn, Albert @Albkat, Christoph @cplett, Thomas @Thomas3R, Ty @TyBalduf

[MtoLStoN]

Currently, xtb-python is no longer in active development and can be seen as more or less in maintenance mode. Therefore, I agree with using tblite as the preferred route for using xtb with Python. I will clarify this in the documentation. Thank you for bringing this to our attention.