add "Snooze" button (add idletimestamp parameter)

[NovemLinguae]

Requested by Asilvering in Discord DM

Why

• sometimes an admin wants to take an unblock request out of CAT:RFU without declining the unblock request, because they are waiting for the blocked user to reply to a question

What

• add a Snooze button
• the existing buttons are red (decline) and blue (accept), so this button should either be blue, or a third color. maybe gray?
• "Snooze" isn't very informative, so put some explanatory text somewhere. on hover, in small text next to it, as an <abbr>, etc. The explanatory text can be something like: "Without accepting or declining, mark that this unblock request is awaiting a reply from the user. This will add |idletimestamp= to the template, and will temporarily take the unblock request out of CAT:RFU until someone replies"
• pressing "Snooze" will add the wikitext |idletimestamp={{subst:CURRENTTIMESTAMP}} to the template. and this will automatically and temporarily move the unblock request out of CAT:RFU and into https://en.wikipedia.org/wiki/Category:Requests_for_unblock_awaiting_response_from_the_blocked_user
• need to detect if this template parameter already exists. if so, need to handle things differently. maybe not show the "Snooze" button at all? or have the "Snooze" button be disabled, and change its text to "Already snoozed"? or have it update the existing |idletimestamp= with a new one?