feat(core): emoji as doc icon support with feature flag (#8348)

close AF-1412

Adjusted the priority of the public doc icon:

1. block-reference
2. journal
3. page reference
4. **emoji** (*new)
5. default

packages/common/infra/src/modules/feature-flag/constant.ts

@@ -104,6 +104,17 @@ export const AFFINE_FLAGS = {
     configurable: true,
     defaultState: true,
   },
+  enable_emoji_doc_icon: {
+    category: 'affine',
+    displayName: 'Emoji Doc Icon',
+    description:
+      'Once enabled, you can use an emoji as the page icon. When the first character of the folder name is an emoji, it will be extracted and used as its icon.',
+    feedbackType: 'discord',
+    feedbackLink:
+      'https://discord.com/channels/959027316334407691/1280014319865696351',
+    configurable: true,
+    defaultState: true,
+  },
   enable_editor_settings: {
     category: 'affine',
     displayName: 'Editor Settings',