Add German language support to config.toml and language switcher

[sba72]

Add German documentation translation initially built from (python/python-docs-de) .

[sba72]

Ok

[StanFromIreland]

Please also prepare a draft PR with:

# Remember to update the Salt config with redirects for new translations!
# For example: https://github.com/python/psf-salt/commit/14bdc3ae054468092e5a8c3cdacfd02f43c32e19

[StanFromIreland]

@sba72 just checking in, if you need any help making the changes please let us know.

[StanFromIreland]

I'm afraid due to the recent movement of some translations to builtins/, you're now at 75% completion of the required articles: https://translations.python.org/#de

Can you please restore the translation?

[hugovk]

For reference, python/cpython#156682 is the move.

[sba72]

Hello, it's done. The changes, new folder /builtin is created, files transferred and new strings in the "must" files are translated.

[StanFromIreland]

Thank you!