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

Source/node_modules/core-js/modules/es6.number.is-nan.js

@@ -0,0 +1,9 @@
+// 20.1.2.4 Number.isNaN(number)
+var $export = require('./_export');
+
+$export($export.S, 'Number', {
+  isNaN: function isNaN(number) {
+    // eslint-disable-next-line no-self-compare
+    return number != number;
+  }
+});