Add option to add internal comment to check

[TimJentzsch]

We already have an internal_comment field for the TranscriptionCheck model, but there is currently no way to modify it.

The best option is probably to add a new "Edit Note" button to the actions, which opens a modal where you can add or edit the note.

The reference for Slack modals is here: https://api.slack.com/surfaces/modals/using
We probably need to check the type of an interactive payload and reroute the request accordingly.
Editing the modal might also be challenging without persisting the view_id to the DB.
We'll have to see if we can implement this stateless.