Improve the Readme

I tried to improve the Readme because many people in my local
chess club do not understand some of the UCO options properly.
Starting point of this was Cfish's Readme by Ronald de Man,
some internet resources and the Stockfish code itself.

Closes https://github.com/official-stockfish/Stockfish/pull/1898

Initial commit by user @erbsenzaehler, with help from users
Adrian Petrescu, @alayan-stk-2 and Elvin Liu.

No functional change

Co-Authored-By: Alayan-stk-2 <alayan-stk-2@users.noreply.github.com>
Co-Authored-By: Adrian Petrescu <apetresc@gmail.com>
Co-Authored-By: Elvin Liu <solarlight2@users.noreply.github.com>