[Glitch] Add categories for custom emojis

Port front-end changes from e64e6a03dd to glitch-soc

Signed-off-by: Thibaut Girka <thib@sitedethib.com>

app/javascript/flavours/glitch/util/emoji/index.js

@@ -93,8 +93,11 @@ export const buildCustomEmojis = (customEmojis) => {
       keywords: [name],
       imageUrl: url,
       custom: true,
+      customCategory: emoji.get('category'),
     });
   });
 
   return emojis;
 };
+
+export const categoriesFromEmojis = customEmojis => customEmojis.reduce((set, emoji) => set.add(emoji.get('category') ? `custom-${emoji.get('category')}` : 'custom'), new Set());