BUG: MessageIsMedia does not check m.new_content

[eyJhb]

When blocking messages there is media, it is possible to bypass if editing the message.
This can be done by sending a new m.room.message with m.new_content being a image type instead (m.image).
This will get posted, without mjolnir reacting to it, and blocking it :)

It seems like MessageIsMedia should recurse into messages, to check for such things.

Hopefully this is the correct way to report it!

EDIT: should clarify, this bypasses everything in the current checker, unless the checker recurses into the message.