Cihai

Breaking changes

The CLI version of `cihai` installed through `cihai-cli` again

- Bump cihai-cli to 0.10.0

And maybe we'll turn cihai into libcihai down the road and remove `cihai[cli]`

Breaking changes

- Python 2 compatibility module and imports removed. Python 2.x was officially
dropped in 0.11.0 (2021-06-15) via 325

- Update `import_string()` and `ImportStringError` to latest from werkzeug
- Use `merge_dict` from `unihan_etl`
- Bump unihan-etl to 0.15.0+ (to avoid any chance of using compat imports from
it in the future)

Compatibility

- Add python 3.10 support (317)
- Remove python 3.6 support (317)

Development

Infrastructure updates for static type checking and doctest examples.

- Update poetry to 1.1
- CI: Use poetry 1.1.12 and `install-poetry.py` installer (296 + 317)
- Relock poetry.lock at 1.1 (w/ 1.1.7's fix)
- Initial [doctests] support added, via 323

[doctests]: https://docs.python.org/3/library/doctest.html

- Initial [mypy] validation, via 323

[mypy]: https://github.com/python/mypy

- CI (tests, docs): Improve caching of python dependencies via
`action/setup-python`'s v3/4's new poetry caching, via 323

- CI (docs): Skip if no `PUBLISH` condition triggered, via 323

Documentation

- Add {ref}`development workflow docs <developing>` (universal to all cihai projects)

- 291: Convert to markdown

- Fix cihai-cli and sqlalchemy versions