4.0 Website Changes (#6193)
* changelog
* fixes to js docs
* add changeset
* change banner to watch
* one off pin for custom components guides
* add changeset
* fix
* add custom components to header
* add small highlight to 4.0 changelog
---------
Co-authored-by: gradio-pr-bot <gradio-pr-bot@users.noreply.github.com>
