Prepare changelog for v3.8.4

CHANGELOG.md

@@ -1,5 +1,14 @@
 # Changelog
 
+## v3.8.4
+
+* Fix margin-top on `<Filter>` that creates an invisible overlay ([5234](https://github.com/marmelab/react-admin/pull/5234)) ([JulienMattiussi](https://github.com/JulienMattiussi))
+* Fix support for function value in `<Form initialValues>` ([5222](https://github.com/marmelab/react-admin/pull/5222)) ([djhi](https://github.com/djhi))
+* Fix  proptypes warning in `<ListToolBar>` ([5230](https://github.com/marmelab/react-admin/pull/5230)) ([zyhou](https://github.com/zyhou))
+* Fix vulnerability in simple example due to `serve` package ([5227](https://github.com/marmelab/react-admin/pull/5227)) ([fzaninotto](https://github.com/fzaninotto))
+* Fix Firefox support in end-to-end tests ([5223](https://github.com/marmelab/react-admin/pull/5223)) ([djhi](https://github.com/djhi))
+* [Doc] Fix changelog typos ([5219](https://github.com/marmelab/react-admin/pull/5219)) ([WiXSL](https://github.com/WiXSL))
+
 ## v3.8.3
 
 * Fix Optimistic Effects Handling ([5212](https://github.com/marmelab/react-admin/pull/5212)) ([djhi](https://github.com/djhi))