Switch to hand-crafted steam autostart

Using the actual steam.desktop starts up the default steam mode, not big
picture, which is what I want. I pulled this content from the
steam.desktop file, so it may need to get adjusted in the far future.

eshu/etc/nixos/configuration.nix

@@ -23,7 +23,20 @@
 
   home-manager.useGlobalPkgs = true;
   home-manager.users.eliribble = { pkgs, ... }: {
-    home.file.".config/autostart/steam.desktop".source = "${pkgs.steam}/share/applications/steam.desktop";
+    home.file.".config/autostart/steam.desktop".text = ''
+    [Desktop Entry]     
+    Name=Steam       
+    Comment=Application for managing and playing games on Steam
+    Exec=steam %U -bigpicture
+    Icon=steam       
+    Terminal=false   
+    Type=Application   
+    Categories=Network;FileTransfer;Game;
+    MimeType=x-scheme-handler/steam;x-scheme-handler/steamlink;
+    Actions=Store;Community;Library;Servers;Screenshots;News;Settings;BigPicture;Friends;
+    PrefersNonDefaultGPU=true
+    X-KDE-RunOnDiscreteGpu=true
+    '';
     # home.packages = [ pkgs.httpie ];
 
     programs.fish.enable = true;