Add support for wl-clipboard for Linux

[sameersharma2006]

Is your feature request related to a problem? Please describe.
I want to use kivy clipboard module in my program but kivy is unable to get any output from a wayland session, i believe this is due to lack of support for wayland compatible clipboard module.

Describe the solution you'd like
Just like xclip, nowadays wl-clipboard is available and is also available in Debian 10 & Ubuntu 20.04, kivy should add support for usability within wayland sessions through wl-clipboard.

Describe alternatives you've considered
Any better and feasible solution to get kivy.clipboard work inside wayland session will be ok.

Additional context
This needs extra focus as Linux is going full on wayland and hence i believe my request is valid.