yuzu_cmd: config: Pass a reference in

Also adds documentation for the ReadSetting function.

Address review comments.

Co-authored-by: Mai M. <mathew1800@gmail.com>

src/yuzu_cmd/config.h

@@ -26,6 +26,12 @@ public:
     void Reload();
 
 private:
+    /**
+     * Applies a value read from the sdl2_config to a BasicSetting.
+     *
+     * @param group The name of the INI group
+     * @param setting The yuzu setting to modify
+     */
     template <typename Type>
-    void ReadSetting(const std::string& group, Settings::BasicSetting<Type> setting);
+    void ReadSetting(const std::string& group, Settings::BasicSetting<Type>& setting);
 };