Lektor-index-pages

- Drop support for Lektor 3.2.x
- Test under python 3.11
- Add type annotations
- Convert packaging from setuptools to [PDM]
- Disuse `pkg_resources` in favor of `importlib.metadata`
- Add [pre-commit] configuration
- Run [black] and [reorder-python-imports] on code

[PDM]: https://pdm.fming.dev/latest/
[pre-commit]: https://pre-commit.com/
[black]: https://black.readthedocs.io/en/stable/index.html
[reorder-python-imports]: https://github.com/asottile/reorder-python-imports

- Drop support for python 2.7 and 3.6.
- Fix deprecation warning from `jinja2`. Jinja2 version 3 is now required.

Documentation

- Documentation clarifications, updates and fixes.
(PR [2][] — Thank you Bart Van Loon!)

- Add missing requirement `recommonmark` to `docs/requirements.txt`.

- Add `docs` enviroment to `tox.ini` to test that docs will build cleanly.

[2]: <https://github.com/dairiki/lektor-index-pages/pull/2>

Testing

- Test under python 3.10 and lektor<3.3

No code changes.

Update development status classifier to "stable".

API changes

- Added a `key` field on the index virtual source object. It is an
alias to `_id`, but is syntactically more self-explanatory.

- The `keys` configuration key has been renamed to `key`.

- When the `key` expression is being evaluted, the record whose key(s)
is(are) to be be computed is now available in the jinja context as
`item` rather than `this`.

Documentation

- Documentation moved from README to Sphinx docs at RTFD.io

API changes

- The `record` argument has been dropped from the (jinja) global
`index_pages` function. (Since indexes can not have multiple
parents, it is not necessary.)

- The `parent` configuration key has been renamed to `parent_path`.

- The `slug` configuration key has been renamed to `slug_format`.

- The `attributes` config section has been renamed to `fields`.

Though they are not quite like regular Lektor Record fields, they
are more field-like than attribute-like. (I.e. access is via
*__getitem__* rather than *getattr*.)

Initial release.