Lazy load components (#3879)

* feat: Lazy-load routes

* feat: Lazy-load modals

* feat: Lazy-load columns

* refactor: Simplify Bundle API

* feat: Optimize bundles

* feat: Prevent flashing the waiting state

* feat: Preload commonly used bundles

* feat: Lazy load Compose reducers

* feat: Lazy load Notifications reducer

* refactor: Move all dynamic imports into one file

* fix: Minor bugs

* fix: Manually hydrate the lazy-loaded reducers

* refactor: Move all dynamic imports to async-components

* fix: Loading modal style

* refactor: Avoid converting the raw state for each lazy hydration

* refactor: Remove unused component

* refactor: Maintain modal name

* fix: Add as=script to preload link

* chore: Fix lint error

* fix(components/bundle): Check if timestamp is set when computing elapsed

* fix: Load compose reducers for the onboarding modal

app/javascript/mastodon/features/ui/containers/bundle_container.js

@@ -0,0 +1,19 @@
+import { connect } from 'react-redux';
+
+import Bundle from '../components/bundle';
+
+import { fetchBundleRequest, fetchBundleSuccess, fetchBundleFail } from '../../../actions/bundles';
+
+const mapDispatchToProps = dispatch => ({
+  onFetch () {
+    dispatch(fetchBundleRequest());
+  },
+  onFetchSuccess () {
+    dispatch(fetchBundleSuccess());
+  },
+  onFetchFail (error) {
+    dispatch(fetchBundleFail(error));
+  },
+});
+
+export default connect(null, mapDispatchToProps)(Bundle);