docs: add shortcut page
A page that shall give quick access to sections in the documentation on commonly used parameters.

Instead of a cheatsheet, it shall just provides refrences preventing the reader from need to bookmark refrence pages or search through the documentation.

This is the idea which is waiting to be converted into a proper PR:
https://github.com/timmie/pandas/blob/9b0932368d6cf608f9e39d14a9532754f672d410/doc/source/shortcuts.rst

If you like to have such a page as well, you can assign me and I will finally prepare the PR.
