feat: code cleanup, new features and v2.0

We're merging this to continue https://github.com/filebrowser/filebrowser/pull/575 and setup translations auto-updating.

src/css/_variables.css

@@ -0,0 +1,7 @@
+:root {
+  --blue: #2196f3;
+  --dark-blue: #1E88E5;
+  --red: #F44336;
+  --dark-red: #D32F2F;
+  --moon-grey: #f2f2f2;
+}