fix(core): display affine icon in lit correctly (#13708)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- New Features
- Added an alternative icon rendering option for document icons,
delivering crisper visuals and consistent emoji/icon display.
- Style
- Improved icon alignment and sizing within grouped icon buttons for
more consistent centering and appearance.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Co-authored-by: Wu Yue <akumatus@gmail.com>

blocksuite/affine/widgets/linked-doc/src/styles.ts

@@ -76,10 +76,16 @@ export const linkedDocPopoverStyles = css`
     border-top: 0.5px solid ${unsafeCSSVarV2('layer/insideBorder/border')};
   }
 
-  .group icon-button svg {
+  .group icon-button svg,
+  .group icon-button .icon {
     width: 20px;
     height: 20px;
   }
+  .group icon-button .icon {
+    display: flex;
+    align-items: center;
+    justify-content: center;
+  }
 
   .linked-doc-popover .group {
     display: flex;