fit-textareas isn't run after a comment submission

[fregante]

Description

The field is cleared either by value = '' or via field.form.reset()

The former doesn't have an event, the latter should be tracked in https://github.com/fregante/fit-textarea

The unfortunate part is that fit-textarea has been in a weird limbo since 1999 so the listener should be added here.

How to replicate the issue + URL

1. Visit an issue
2. Smash the keyboard and enter enough line breaks to expand the field
3. Submit comment
4. Notice that the field doesn't shrink back

Extension version

23.4.15

Browser(s) used

Safari, Chrome