Use GTK titlebars

When running under a Wayland compositor Alacritty will draw its own titlebar. To have it use the GTK one we need to force it to draw under X11 by setting the WINIT_UNIX_BACKEND environment variable. We can modify Alacritty.desktop for this:

--- /usr/share/applications/Alacritty.desktop 2022-11-16 16:11:46.000000000 +0000
+++ /home/lukecarrier/.local/share/applications/Alacritty.desktop 2022-11-17 21:58:03.491830911 +0000
@@ -1,7 +1,7 @@
 [Desktop Entry]
 Type=Application
 TryExec=alacritty
-Exec=alacritty
+Exec=env WINIT_UNIX_BACKEND=x11 alacritty
 Icon=Alacritty
 Terminal=false
 Categories=System;TerminalEmulator;
@@ -16,4 +16,4 @@

 [Desktop Action New]
 Name=New Terminal
-Exec=alacritty
+Exec=env WINIT_UNIX_BACKEND=x11 alacritty