Add 4 new browser snippets

triggerEvent - trigger an event on an element, insertAfter & insertBefore - parse and insert HTML after or before an element respectively, elementContains - checks if an element contains another element

test/insertBefore/insertBefore.js

@@ -0,0 +1,2 @@
+const insertBefore = (el, htmlString) => el.insertAdjacentHTML('beforebegin', htmlString);
+module.exports = insertBefore;