feat(leaderboard): add leaderboard functionaltiy

src/types/leaderboard.ts

@@ -0,0 +1,13 @@
+export type LeaderboardEntry = {
+  rank: number;
+  user_id: string;
+  name: string;
+  avatar_url: string;
+  total_xp: number;
+  current_level: number;
+};
+
+export interface Leaderboard {
+  top_users: LeaderboardEntry[];
+  user_rank: LeaderboardEntry;
+}