xclip.el & WSL

[Justin Abrahms]

Hey folks,

Looking through the xclip.el source and noticed the comment ";FIXME: How 
do we detect WSL?". There are official answers in this thread: 
https://github.com/microsoft/WSL/issues/4071 . My favorite answer is 
that "uname -r" contains the word microsoft. Mine says: 
5.15.90.1-microsoft-standard-WSL2

Additionally, there is a bug whereby the xclip-program variable is set 
to "powershell" the defcustom, but the actual value needs to be 
"clip.exe". I've overridden it in my config, but seems like someone 
should fix it for the next person.

-justin