docs(glossary): promises point to dead link, update to mozilla link

closes #1365

Author: kylerob

public/docs/ts/latest/glossary.jade

@@ -683,7 +683,8 @@ include _util-fns
 
     The browser DOM and JavaScript have a limited number
     of asynchronous activities, activities such as DOM events (e.g., clicks),
-    [promises](#promise), and
+    [promises](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/
+    Promise), and
     [XHR](https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest)
     calls to remote servers.