dankinstall: set default niri config with includes

core/internal/config/embedded/niri-layout.kdl

@@ -0,0 +1,17 @@
+layout {
+    gaps 4
+
+    border {
+        width 2
+    }
+
+    focus-ring {
+        width 2
+    }
+}
+window-rule {
+    geometry-corner-radius 12
+    clip-to-geometry true
+    tiled-state true
+    draw-border-with-background false
+}