Add page on alternatives to Wayland-incompatible Xorg apps

[gianklug]

Could also be added to the frontpage.

Example: User wants a replacement for xrandr -> ngw-displays/wdisplays

[kekkoudesu]

It might be worth considering whether the Wayland alternative works on all Wayland compositors.

For example, grim and slurp work well as a drop-in replacement for similarly simple screen capture utilities on X, but they only support Sway.

Or most compositors don't implement a built-in alternative to xkill, but KDE has a shortcut mapped to CTRL+META+ESC that does exactly this.

[gianklug]

The technical implementation for alternatives was added here: 5ed2ff4

I'll maybe add labels for compositor support later.