DOC: consider adding chapter Known Limitations

[remkop]

Follow-up from suggestion by @deining in discussion here: #1297 (comment)

Repeating some key contents:

I reflected on adding a new chapter 22. Known limitations and caveats that list (amongst others) the limitation of nested classes. Despite we have admonitions now in various places, I tend to think this still would be an enhancement to the documentation.

(...) Between "Tips & Tricks" and "Dependency Injection" is probably a good insertion point.
I like short titles, how about just "Known Limitations"?

Some limitations are already documented, like Variable Arity Limitations, Argument Group Limitations, Limitations of Variable Interpolation, default values for annotated fields, interactive positional parameters, Optional Parameter Limitations.

For some of these it may make sense to repeat the content or expand on the content with an example, for other limitations that already have extensive documentation, perhaps we can just link from the new chapter to the existing section.