Do something with "replies" feature

[mrphlip]

Twitch just added an ability to "thread" chat messages as replies to other chat messages.

We should consider doing something with these... possibly: (a) turning replies to chat commands into threaded replies (b) recognising incoming threaded replies in some way in the chatlog

Technical details:

Sending:

@reply-parent-msg-id=[uuid] PRIVMSG #channel :[message]

Receiving:

@reply-parent-display-name=[display name of parent poster];reply-parent-msg-body=[text of parent message];reply-parent-msg-id=[uuid];reply-parent-user-id=[numerical id of parent poster];reply-parent-user-login=[login id of parent poster] PRIVMSG #channel :@[display name of parent poster] [message]

(in addition to all the other usual message tags)

Notes:

• The received message has @username prepended, for the benefit of IRC clients, and the Twitch web chat removes this on display, since it's redundant with the "in reply to" label.
• When replying to a reply, the reply-parent-msg-id is always referring to the head of the reply chain. So if A posts, then B replies to A, then C replies to B, then D replies to C... all those replies will reference A's msg-id, and have A's message details in the other fields. They'll also all have @A prepended to the message.
• This feature does not appear to be active on #loadingreadyrun as yet, so any implementation will have to wait until it's active there. If you want to test things, feel free to experiment on #cusk_assbiefef, because while it's not active on my channel either, it is active on my scratch-testing alt.

Sample:

<<< @badge-info=;badges=broadcaster/1;color=;display-name=cusk_assbiefef;emotes=;flags=;id=ce421efa-106d-40f7-8f2f-416541a71433;mod=0;room-id=150631270;subscriber=0;tmi-sent-ts=1597133706030;turbo=0;user-id=150631270;user-type= :cusk_assbiefef!cusk_assbiefef@cusk_assbiefef.tmi.twitch.tv PRIVMSG #cusk_assbiefef :This is a test message
>>> @reply-parent-msg-id=ce421efa-106d-40f7-8f2f-416541a71433 PRIVMSG #cusk_assbiefef :This is a reply to the test
<<< @badge-info=;badges=broadcaster/1;color=;display-name=cusk_assbiefef;emotes=;flags=;id=cc1b5192-f5dd-40cf-b33f-757a28607226;mod=0;reply-parent-display-name=cusk_assbiefef;reply-parent-msg-body=This\sis\sa\stest\smessage;reply-parent-msg-id=ce421efa-106d-40f7-8f2f-416541a71433;reply-parent-user-id=150631270;reply-parent-user-login=cusk_assbiefef;room-id=150631270;subscriber=0;tmi-sent-ts=1597133724458;turbo=0;user-id=150631270;user-type= :cusk_assbiefef!cusk_assbiefef@cusk_assbiefef.tmi.twitch.tv PRIVMSG #cusk_assbiefef :@cusk_assbiefef This is a reply to the reply