* add `typing-extensions` dev dependency
* make sure `Self` import falls back to `typing-extensions`
* let setuptools find sub-packages
* pass global `Application` instance to cli commands
* move `RELAY_SOFTWARE` to relay/misc.py
* allow `str` for `follow` in `Message.new_unfollow`

* get actor url from incoming message
* fall back to actor inbox if there is no shared inbox

* rename `register_route` to `register_view`
* add `register_route` function
* convert frontend and misc routes to use `register_route`

version 0.3.3

See merge request !59

* raise `blib.HttpError` on non 200 and 202 statuses
* use `EmptyBodyError` instead of `ValueError` for empty bodies