Proton support (#64)

Enable proton for heroic games

src/gog/gog_game.rs

@@ -25,6 +25,7 @@ pub(crate) struct PlayTask {
     pub working_dir: Option<String>,
 }
 
+#[derive(Clone)]
 pub(crate) struct GogShortcut {
     pub name: String,
     pub game_folder: String,

src/gog/gog_platform.rs

@@ -149,6 +149,13 @@ impl Platform<GogShortcut, GogErrors> for GogPlatform {
             },
         }
     }
+
+    fn needs_proton(&self, _input: &GogShortcut) -> bool {
+            #[cfg(target_family = "unix")]
+            return true;
+            #[cfg(target_os = "windows")]
+            return false;
+    }
 }
 
 #[cfg(target_family = "unix")]