Add shortcuts to messages

[violine1101]

This PR simply adds very short shortcuts to messages (well, all except for the bot message, I didn't see any point in adding it there).

I'm currently transferring over my workflow to use the helper messages repo instead, so I no longer need to maintain a separate copy of the helper messages database.

The reason for adding the shortcuts is to be able to easily input a message into a Mojira text field without the need to visit the external webpage. For instance, when I type "mji-dup", it will expand to the full helper message.

Until now I used a third-party browser extension to do this, however it doesn't work too well and had a few more downsides, so I'm currently in the process of developing a custom browser extension that always stays in sync with the messages from this repo. I'm looking forward to sharing that with you all as well when it's ready.

[Marcono1234]

@violine1101, would it make sense to mark messages which are only intended for Arisa? E.g. for i-am-a-bot and not-reopen-ar it would not make sense if a staff member used it.

[violine1101]

Yeah, I already restricted i-am-a-bot to mctest in #62, so that it doesn't clutter up the list. Perhaps it would be a good idea to introduce a type field in the future, so that we can distinguish messages, panels, and bot messages.