Document the add-global/ module

This adds docs for add-global, will go into canjs/canjs.

add-global.md

@@ -0,0 +1,16 @@
+@module {function} can-event-dom-enter/add-global/add-global can-event-dom-enter/add-global/add-global
+@parent can-event-dom-enter
+@description
+
+Registers a global `enter` event, allowing listening to enter anywhere in your application.
+
+@signature `unregister()`
+
+Importing `can-event-dom-enter/add-global/add-global` registers the __enter__ event globally. Calling `unregister()` removes it from the global registry.
+
+```js
+import unregister from 'can-event-dom-enter/add-global/add-global';
+
+// Later time
+unregister();
+```

can-event-dom-enter.js

@@ -13,6 +13,7 @@ function isEnterEvent (event) {
  * @module {events} can-event-dom-enter
  * @parent can-dom-utilities
  * @collection can-infrastructure
+ * @group can-event-dom-enter.modules modules
  * @package ./package.json
  *
  * Watch for when enter keys are pressed on a DomEventTarget.