fix(editor): footnote popup style and position issues (#11771)

Close [BS-3049](https://linear.app/affine-design/issue/BS-3049/chat引用的样式坏了) [BS-3024](https://linear.app/affine-design/issue/BS-3024/footnote-在容器边缘时，hover-抽搐)

blocksuite/affine/inlines/reference/src/reference-node/reference-node.ts

@@ -49,6 +49,10 @@ export class AffineReference extends WithDisposable(ShadowlessElement) {
       cursor: pointer;
       user-select: none;
       padding: 1px 2px 1px 0;
+
+      svg {
+        margin-bottom: 0.1em;
+      }
     }
     .affine-reference:hover {
       background: var(--affine-hover-color);