Add onAfterDestroy callback description to react docs

[Mati365]

Suggested merge commit message (convention)

Docs: Add onAfterDestroy callback description to React integration docs.

Why has been this callback introduced?

1. Editor uses async destroy method that does not work super fine with React lifecycle.
2. Editor is most of the time destroyed after unmounting of component or changing its ID property.
3. This callback makes sure that all side effects (such as added editable HTML DOM nodes) are removed after destroying all plugins attached to the editor.
4. onAfterDestroy is being batched, so in other words rapid id change (10 in row) will trigger only ~1 call of this callback which prevents race conditions in Strict Mode.

Additional information

1. The onAfterDestroy callback has been added in this commit in our React integration.
2. It's not released yet at this moment (20.05.2024).

[Mati365]

Thank you @godai78.

@pomek Can you merge it after release of React integration?

fyi @scofalik

[pomek]

Except for the mentioned things, please target the PR to the #stable branch if we aim to deploy these changes without waiting until the next release.

[Mati365]

@pomek It can be deployed in normal flow I think. There is no need to deploy it instantly after merge because this callback is not critical to work with integration (especially because it was not present for years). Thanks for suggestion to docs anyway.

[scofalik]

LGTM, you can merge it. As far as I understand, neither the new callback nor the docs for the callback are going to be released in this release (which should happen very shortly)?

[pomek]

The required package has been released (https://github.com/ckeditor/ckeditor5-react/releases/tag/v7.0.0).

[godai78]

We have ported these changes to new installation docs, which we plan on merging to master sometime soon, so this will be wvisible on nightly.