refactor(core): split web entry from core (#6082)

This pr is trying to split `web` and `electron` entries from `core`. It allows more platform-related optimization to be addressed in each entry.
We should remove all browser/electron only codes from `core` eventually, this is the very first step for that.

packages/frontend/web/src/polyfill/resize-observer.ts

@@ -0,0 +1,8 @@
+import { ResizeObserver } from '@juggle/resize-observer';
+
+// prevents the following error in development mode:
+// ResizeOvserver loop limit exceeded
+// https://github.com/petyosi/react-virtuoso/issues/875#issuecomment-1962897033
+if (process.env.NODE_ENV !== 'production') {
+  window.ResizeObserver = ResizeObserver;
+}