modularize niri config

configs/niri/base/noctalia-shell.kdl

@@ -0,0 +1,16 @@
+window-rule {
+  // Rounded corners for a modern look.
+  geometry-corner-radius 20
+  // Clips window contents to the rounded corner boundaries.
+  clip-to-geometry true
+}
+debug {
+  // Allows notification actions and window activation from Noctalia.
+  honor-xdg-activation-with-invalid-serial
+}
+// Set the overview wallpaper on the backdrop.
+layer-rule {
+  match namespace="^noctalia-overview*"
+  place-within-backdrop true
+}
+