default-config: Add rounded corner window rule example

resources/default-config.kdl

@@ -250,6 +250,13 @@ window-rule {
     // block-out-from "screencast"
 }
 
+// Example: enable rounded corners for all windows.
+// (This example rule is commented out with a "/-" in front.)
+/-window-rule {
+    geometry-corner-radius 12
+    clip-to-geometry true
+}
+
 binds {
     // Keys consist of modifiers separated by + signs, followed by an XKB key name
     // in the end. To find an XKB name for a particular key, you may use a program