Add reply support to all message types

.gitignore

include/mtx/events/messages/audio.hpp

include/mtx/events/messages/emote.hpp

include/mtx/events/messages/file.hpp

include/mtx/events/messages/image.hpp

include/mtx/events/messages/video.hpp

lib/structs/events/messages/audio.cpp

lib/structs/events/messages/emote.cpp

lib/structs/events/messages/file.cpp

lib/structs/events/messages/image.cpp

lib/structs/events/messages/video.cpp

tests/messages.cpp