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

Source/node_modules/core-js/modules/es6.math.cosh.js

@@ -0,0 +1,9 @@
+// 20.2.2.12 Math.cosh(x)
+var $export = require('./_export');
+var exp = Math.exp;
+
+$export($export.S, 'Math', {
+  cosh: function cosh(x) {
+    return (exp(x = +x) + exp(-x)) / 2;
+  }
+});