refactor: add 'stores' folder and move challenges store

src/stores/use-challenges-store.ts

@@ -0,0 +1,24 @@
+import { create } from 'zustand';
+import { Challenge } from '@plebbit/plebbit-react-hooks';
+
+interface State {
+  challenges: Challenge[];
+  addChallenge: (challenge: Challenge) => void;
+  removeChallenge: () => void;
+}
+
+const useChallengesStore = create<State>((set) => ({
+  challenges: [],
+  addChallenge: (challenge: Challenge) => {
+    set((state) => ({ challenges: [...state.challenges, challenge] }));
+  },
+  removeChallenge: () => {
+    set((state) => {
+      const challenges = [...state.challenges];
+      challenges.shift();
+      return { challenges };
+    });
+  },
+}));
+
+export default useChallengesStore;