Added proton GE as a steam compat tool

modules/apps/steam/default.nix

@@ -24,5 +24,13 @@ in {
       driSupport = true;
       driSupport32Bit = true;
     };
+
+    # TODO: This can be removed when/if PR 189398 is merged
+    # https://github.com/NixOS/nixpkgs/pull/189398
+    aa.home.extraOptions = {
+      home.sessionVariables = {
+        STEAM_EXTRA_COMPAT_TOOLS_PATHS = "${pkgs.aa.proton-ge-custom}";
+      };
+    };
   };
 }

packages/proton-ge-custom/default.nix

@@ -0,0 +1,20 @@
+{
+  stdenv,
+  lib,
+  fetchurl,
+  ...
+}:
+stdenv.mkDerivation rec {
+  pname = "proton-ge-custom";
+  version = "GE-Proton8-11";
+
+  src = fetchurl {
+    url = "https://github.com/GloriousEggroll/proton-ge-custom/releases/download/${version}/${version}.tar.gz";
+    sha256 = "sha256-ldJBwp/9Cjb5k9FBrc6iz4/rnMhU5Ayf35+kNTAvXCg=";
+  };
+
+  buildCommand = ''
+    mkdir -p $out
+    tar -C $out --strip=1 -x -f $src
+  '';
+}