lutris: add extraLibraries/extraPkgs args

steam has extraLibraries and extraPkgs arguments which allow the user
to define additional libraries and software which may be required to
run their Steam software.

This commit simply add the same mechanic to lutris.

pkgs/applications/misc/lutris/fhsenv.nix

@@ -1,4 +1,6 @@
 { lib, buildFHSUserEnv, lutris-unwrapped
+, extraPkgs ? pkgs: [ ]
+, extraLibraries ? pkgs: [ ]
 , steamSupport ? true
 }:
 
@@ -87,7 +89,8 @@ in buildFHSUserEnv {
     soundfont-fluid bzip2 game-music-emu
   ] ++ qt5Deps pkgs
     ++ gnomeDeps pkgs
-    ++ lib.optional steamSupport pkgs.steam;
+    ++ lib.optional steamSupport pkgs.steam
+    ++ extraPkgs pkgs;
 
   multiPkgs = pkgs: with pkgs; [
     # Common
@@ -110,7 +113,8 @@ in buildFHSUserEnv {
 
     # Winetricks
     fribidi
-  ] ++ xorgDeps pkgs;
+  ] ++ xorgDeps pkgs
+    ++ extraLibraries pkgs;
 
   extraInstallCommands = ''
     mkdir -p $out/share