Minor edits to niri.

.config/niri/config.kdl

@@ -169,6 +169,11 @@ animations {
 }
 
 // Window rules let you adjust behavior for individual windows.
+window-rule {
+    match title="VirtualBox"
+    open-fullscreen true
+}
+
 window-rule {
     // This app-id regular expression will work for both:
     // - host Firefox (app-id is "firefox")