desktop file: use dynamic value for desc instead of hardcoded one

Author: Totto16

assets/oopetris.desktop.in

@@ -2,7 +2,7 @@
 Version=1.0
 Type=Application
 Name=OOPetris
-Comment=A Tetris clone in OOP
+Comment=@DESCRIPTION@
 Exec=oopetris
 Icon=@APP_NAME@
 Terminal=false

tools/install/meson.build

@@ -13,8 +13,7 @@ if is_flatpak_build
     app_name = 'com.github.mgerhold.OOPetris'
 endif
 
-conf = configuration_data()
-conf.set('APP_NAME', app_name)
+conf = configuration_data({'DESCRIPTION': oopetris_desc, 'APP_NAME': app_name})
 
 datadir = get_option('prefix') / get_option('datadir')