docs: extend patterns understood by bothify📃

[KarelZe]

What does this change

This PR extends the documentation for bothify(). Previously, the docs only documented the placeholders # for numerics. Which gave the impression, that the scope of bothify() is limited compared to numerify(). However, all patterns of numerify() are possible.

What was wrong

Docs for numerify() and bothify() were just out-of-sync.

How this fixes it

Docs now show all valid patterns and samples have been extended.

Checklist

• [x] I have read the documentation about CONTRIBUTING
• [x] I have read the documentation about Coding style
• [x] I have run make lint