Frontent dev env (#247)

* Added frontend development files/environment

* More items-categories related removals

* Improvements in pages templates (inc. static pages)

* Improvements in video player

* Added empty home page message + cta

* Updates in media, playlist and management pages

* Improvements in material icons font loading

* Replaced media & playlists links in frontend dev-env

* frontend package version update

* chnaged frontend dev url port

* static files update

* Changed default position of theme switcher

* enabled frontend docker container

frontend/src/static/js/utils/helpers/imageExtension.js

@@ -0,0 +1,7 @@
+export const imageExtension = (img) => {
+  if (!img) {
+    return;
+  }
+  const ext = img.split('.');
+  return ext[ext.length - 1];
+};