defined class .growi-bot-kun

src/client/styles/scss/_admin.scss

@@ -137,6 +137,10 @@ $slack-work-space-name-card-border: #efc1f6;
       background-color: $slack-work-space-name-card-background;
       border: 1px solid $slack-work-space-name-card-border;
     }
+    .growi-bot-kun {
+      width: 20px;
+      height: 20px;
+    }
   }
 
   //// TODO: migrate to Bootstrap 4