feat(main): Add base theme: This is the falcon theme out of the box.

This is falcon v3.1.2

falcon/_dev/js/theme/components/PageLoader.js

@@ -0,0 +1,17 @@
+import $ from 'jquery';
+
+class PageLoader {
+  constructor() {
+    this.$body = $('body');
+  }
+
+  showLoader() {
+    this.$body.addClass('page-loader-active');
+  }
+
+  hideLoader() {
+    this.$body.removeClass('page-loader-active');
+  }
+}
+
+export default PageLoader;