Adding Room Key Verification Stuff

include/mtx/events.hpp

include/mtx/events/collections.hpp

include/mtx/events/encrypted.hpp

include/mtx/secret_storage.hpp

lib/structs/events.cpp

lib/structs/events/collections.cpp

lib/structs/events/encrypted.cpp

lib/structs/responses/common.cpp

lib/structs/responses/crypto.cpp