Add support for multiple Steam library directories

data/gtk/preferences.blp

@@ -30,6 +30,30 @@ template PreferencesWindow : Adw.PreferencesWindow {
           valign: center;
         }
       }
+      Adw.ActionRow {
+        title: _("Extra Steam Libraries");
+        subtitle: _("Select other directories where you have Steam games installed");
+
+
+        Revealer steam_clear_button_revealer {
+          reveal-child: false;
+          transition-type: slide_left;
+          Button steam_clear_button {
+            label: _("Clear");
+            valign: center;
+            halign: end;
+
+            styles [
+              "destructive-action",
+            ]
+          }
+        }
+
+        Button steam_extra_file_chooser_button {
+          icon-name: "folder-new-symbolic";
+          valign: center;
+        }
+      }
     }
 
     Adw.PreferencesGroup heroic_group {