chore: Add cache to improve widget performance (#11163)

- Add dynamic importing for routes.
- Added caching for `campaign`, `articles` and `inbox_members` API end
points.

---------

Co-authored-by: Pranav <pranavrajs@gmail.com>

app/javascript/shared/helpers/cache.js

@@ -0,0 +1,43 @@
+import { LocalStorage } from './localStorage';
+
+// Default cache expiry is 24 hours
+const DEFAULT_EXPIRY = 24 * 60 * 60 * 1000;
+
+export const getFromCache = (key, expiry = DEFAULT_EXPIRY) => {
+  try {
+    const cached = LocalStorage.get(key);
+    if (!cached) return null;
+
+    const { data, timestamp } = cached;
+    const isExpired = Date.now() - timestamp > expiry;
+
+    if (isExpired) {
+      LocalStorage.remove(key);
+      return null;
+    }
+
+    return data;
+  } catch (error) {
+    return null;
+  }
+};
+
+export const setCache = (key, data) => {
+  try {
+    const cacheData = {
+      data,
+      timestamp: Date.now(),
+    };
+    LocalStorage.set(key, cacheData);
+  } catch (error) {
+    // Ignore cache errors
+  }
+};
+
+export const clearCache = key => {
+  try {
+    LocalStorage.remove(key);
+  } catch (error) {
+    // Ignore cache errors
+  }
+};