add user directory search

CMakeLists.txt

include/mtx/events_impl.hpp

include/mtx/requests.hpp

include/mtx/responses.hpp

include/mtx/responses/users.hpp

include/mtxclient/crypto/objects.hpp

include/mtxclient/http/client.hpp

lib/http/client.cpp

lib/structs/requests.cpp

lib/structs/responses/users.cpp

meson.build

tests/client_api.cpp

tests/requests.cpp

tests/responses.cpp