Display global KDE Plasma theme and fix bug with DE listing on windows

[mcneb10]

Description

The global KDE Plasma theme wasn't included in the neofetch theme listing, so I decided to add it if the program can find it.

Screenshots

Before:

After:

[mcneb10]

I also fixed a bug where on Windows, neofetch would try to get $XDG_SESSION_TYPE, which always fails, resulting in empty parentheses after the DE Name
Before:
DE: Fluent ()
After:
DE: Fluent

[hykilpikonna]

Thanks!