DEV: port sidebar new topic component into theme (#129)

This moves the [sidebar new topic button
component](https://github.com/discourse/discourse-sidebar-new-topic-button)
into the theme directly

If you have installed this theme previously, you should manually remove
the component.

javascripts/discourse/api-initializers/sidebar-new-topic-button-connector.js

@@ -0,0 +1,6 @@
+import { apiInitializer } from "discourse/lib/api";
+import SidebarNewTopicButton from "../components/sidebar-new-topic-button";
+
+export default apiInitializer("1.8.0", (api) => {
+  api.renderInOutlet("before-sidebar-sections", SidebarNewTopicButton);
+});