Broke up UI into seperate file, reorganisation of dirtree, added ViewStack

data/resources/ui/settings.blp

@@ -0,0 +1,12 @@
+using Gtk 4.0;
+using Adw 1;
+
+template $SettingsPage: Box {
+  Adw.Clamp {
+    Box {
+      Text {
+        text: _("This is a placeholder!");
+      }
+    }
+  }
+}