Implement UI event dispatcher/listener (#76)

in-app-manual/plugins/uipluginapi.md

@@ -150,4 +150,12 @@ Registers an after function. An after function is called after the render functi
 | `component` | `string` | The name of the component to patch. |
 | `fn` | `Function` | The after function. It accepts the same arguments as the original render function, plus the result of the original render function, and is expected to return the rendered component. |
 
-Returns `void`.
+Returns `void`.
+
+#### `PluginApi.Event`
+
+Allows plugins to listen for Stash's events.
+
+```js
+PluginApi.Event.addEventListener("stash:location", (e) => console.log("Page Changed", e.detail.data.location.pathname))
+```