Refactoring monitor layout for rofi

[rememberYou]

First of all, I want to thank you for your work. I allowed myself to refactor the code for the monitor_layout.sh script.

This refactorization includes:

• Adding global documentation
• Deleting unnecessary variables.
• Display correction for dual screen: it is more logical that (A -> B) means that A is to the left of B.
• Better display by adding two points after the number (0 Cancel -> 0: Cancel).
• Redundant code reduction.
• Arrows with Font Awesome 5 (can be removed if you want to avoid dependencies).

NOTE: before accepting this pull request, it would first be wise to first accept this one

My apologies for the reversal of order.