Refactor alerts to TypeScript, remove react-notification dependency (#34239)

app/javascript/mastodon/reducers/alerts.ts

@@ -0,0 +1,24 @@
+import { createReducer } from '@reduxjs/toolkit';
+
+import { showAlert, dismissAlert, clearAlerts } from 'mastodon/actions/alerts';
+import type { Alert } from 'mastodon/models/alert';
+
+const initialState: Alert[] = [];
+
+let id = 0;
+
+export const alertsReducer = createReducer(initialState, (builder) => {
+  builder
+    .addCase(showAlert, (state, { payload }) => {
+      state.push({
+        key: id++,
+        ...payload,
+      });
+    })
+    .addCase(dismissAlert, (state, { payload: { key } }) => {
+      return state.filter((item) => item.key !== key);
+    })
+    .addCase(clearAlerts, () => {
+      return [];
+    });
+});