feat: add animation for emoji panel (#85)

为 Emoji 选择组件添加展开动画。

/kind improvement

```release-note
None
```

Author: ruibaby

packages/comment-widget/src/emoji-button.ts

@@ -129,13 +129,26 @@ export class EmojiButton extends LitElement {
         box-shadow: 0 0.5em 1em rgba(0, 0, 0, 0.1);
         border-radius: 0.875em;
         overflow: hidden;
+        animation: fadeInUp 0.3s both;
       }
 
       @media (max-width: 640px) {
         .form__emoji-panel {
           right: -7.8em;
         }
       }
+
+      @keyframes fadeInUp {
+        from {
+          opacity: 0;
+          transform: translate3d(0, 5%, 0);
+        }
+
+        to {
+          opacity: 1;
+          transform: translate3d(0, 0, 0);
+        }
+      }
     `,
   ];
 }