Added support for "messageTypeID = submysterygift"

[fmalk]

I started receiving this new kind of UserNoticeMessage and I wanted a method like isSub() et al to deal with this type of message.

So I added a new MassSubgiftUsernoticeMessage, just like other SpecificUsernoticeMessage.

I've added a unit test as well. There's a new eventParam called massGiftCount that should be present.

[RAnders00]

Hey, the build doesn't pass on this PR because you didn't run the automatic formatter (npm run precommit). Would you mind doing that and pushing the changes, so I can take another look? Thank you!

[fmalk]

@RAnders00 there you go, it should pass lint tests now