version handling and typestore

Since 9.20 (https://ternaris.gitlab.io/rosbags/changes.html) a global typestore is no longer available.

Need to either pin version lower or handle the ROS-distro-specific typestore stuff

• Add pyproject.toml / poetry.lock
  • See if easy way we can get deps recursively? Would be nice if this propogated automatically to users of ros_datahandler
• Check that the user msgs can be loaded