Developer tooling for building/testing jupyter artifacts

[tonyfast]

• moves some existing doit logic in to a jupyter_accessibility module.
  • the module builds environments, jupyter assets, executes tests, and imports test results
• adds ci for accessibility tests.

[tonyfast]

the last iterations add:

• ci for the project
• a bunch of docstrings and documentation
• the ability to build/test for both pypi and git

[tonyfast]

the things this pull request is missing and should be addressed:

• the doit task logic. currently we have to compose the doit tasks ourselves. using dependencies and create_after we should be able to have a single command for everything
• developer docs and documentation.
• integration in the jupyter cli
• separate javascript testing package from the python packages

[gabalafou]

Let's close this PR in favor of #90?