feat: Change the bubble padding in style settings

lib/pages/settings_style/settings_style.dart

@@ -86,6 +86,14 @@ class SettingsStyleController extends State<SettingsStyle> {
         );
   }
 
+  void changeBubbleSizeFactor(double d) {
+    setState(() => AppConfig.bubbleSizeFactor = d);
+    Matrix.of(context).store.setItem(
+          SettingKeys.bubbleSizeFactor,
+          AppConfig.bubbleSizeFactor.toString(),
+        );
+  }
+
   @override
   Widget build(BuildContext context) => SettingsStyleView(this);
 }