Add comments about JS removal of message query_arg

[davidsword]

This is a follow-up to #23367.

Can someone please add some inline doc about how Javascript actually removes &message=x from the URL - Specifically in /wp-admin/edit-form-advanced.php:186 (in WP 4.9.1).

As a plugin developer who looks up source code for solutions, I was wracking my brain around seeing $_GET['message'] as the main argument for showing admin notices, but never seeing it in backend. Took unnecessarily long time to figure out it actually exists and is just hidden.

[davidbaumwald]

@davidsword Thanks for the ticket! This technically is not related to the Comments component and pertains to docs-type comments, which I think is what you're requesting. Setting the component to Administration so it can be picked up by that group.

Specifically looking at this issue, it seems the needs to document this a bit better was realized back in [25819].

Trac ticket: https://core.trac.wordpress.org/ticket/42952