feat(shared/hm): add vkcapture obs plugin and use it in game launch script

shared/home-manager/dotfiles/obs-studio.nix

@@ -6,7 +6,13 @@
     plugins = with pkgs.obs-studio-plugins; [
       input-overlay
       obs-backgroundremoval
+      obs-gstreamer
       obs-pipewire-audio-capture
+      obs-vkcapture
     ];
   };
+
+  home.packages = [
+    pkgs.obs-studio-plugins.obs-vkcapture
+  ];
 }

shared/home-manager/scripts/games/launch.sh

@@ -4,4 +4,4 @@
 # but there might be useful ones in the future.
 # https://docs.mesa3d.org/envvars.html
 
-mangohud gamemoderun "$@"
+obs-gamecapture mangohud gamemoderun "$@"