Add extracted source directory and README navigation

extracted-source/node_modules/qrcode/lib/can-promise.js

@@ -0,0 +1,7 @@
+// can-promise has a crash in some versions of react native that dont have
+// standard global objects
+// https://github.com/soldair/node-qrcode/issues/157
+
+module.exports = function () {
+  return typeof Promise === 'function' && Promise.prototype && Promise.prototype.then
+}