Completely integrate wepack in django

* Migrate alpine
* Migrate jquery and jquery-ui
* Migrate shorten
* Add babel for javascript
* Introduce staticfiles django app
* Only bundle -index.js files in static/webpack
* Unify scss and webpack generated files
* Convert scss calls to static
* Add --clear-generated option to collectstatic
* Fix docs warnings

core/static/webpack/alpine-index.js

@@ -0,0 +1,7 @@
+import Alpine from "alpinejs";
+
+window.Alpine = Alpine;
+
+addEventListener("DOMContentLoaded", (event) => {
+  Alpine.start();
+});

core/static/webpack/easymde-index.js

@@ -0,0 +1,5 @@
+import "codemirror/lib/codemirror.css";
+import "easymde/src/css/easymde.css";
+import EasyMDE from "easymde";
+
+window.EasyMDE = EasyMDE;

core/static/webpack/jquery-index.js

@@ -0,0 +1,25 @@
+import $ from "jquery";
+import "jquery.shorten/src/jquery.shorten.min.js";
+
+// We ship jquery-ui with jquery because when standalone with webpack
+// JQuery is also included in the jquery-ui package. We do gain space by doing this
+// We require jquery-ui components manually and not in a loop
+// Otherwise it increases the output files by a x2 factor !
+require("jquery-ui/ui/widgets/accordion.js");
+require("jquery-ui/ui/widgets/autocomplete.js");
+require("jquery-ui/ui/widgets/button.js");
+require("jquery-ui/ui/widgets/dialog.js");
+require("jquery-ui/ui/widgets/tabs.js");
+
+require("jquery-ui/themes/base/all.css");
+
+/**
+ * Simple wrapper to solve shorten not being able on legacy pages
+ * @param {string} selector to be passed to jQuery
+ * @param {Object} options object to pass to the shorten function
+ **/
+export function shorten(selector, options) {
+  $(selector).shorten(options);
+}
+
+window.shorten = shorten;