First support for md extensions; Package all needed dependencies in the repo

Source/node_modules/core-js/modules/es7.string.trim-right.js

@@ -0,0 +1,7 @@
+'use strict';
+// https://github.com/sebmarkbage/ecmascript-string-left-right-trim
+require('./_string-trim')('trimRight', function ($trim) {
+  return function trimRight() {
+    return $trim(this, 2);
+  };
+}, 'trimEnd');