Don't override Dom7 methods if already declared

I'm using dom7 modular in a project together with swiper and patched some methods to be more jquery compatible (e.g. added second argument for toggleClass).

src/utils/dom.js

@@ -80,7 +80,7 @@ const Methods = {
 };
 
 Object.keys(Methods).forEach((methodName) => {
-  $.fn[methodName] = Methods[methodName];
+  $.fn[methodName] = $.fn[methodName] || Methods[methodName];
 });
 
 export default $;