Mddj

- Fix handling of `tox.ini` data to support reading python versions with a dot,
as in `py3.8,py3.9`

- Fix a bug which caused `mddj read tox list-versions` to contain duplicates
for certain configs

- Add `mddj self version` command to see the current `mddj` version

- Initial commands in support of reading `tox.ini` data (via subprocess
invocation of `tox`): `mddj read tox min-version` and
`mddj read tox list-versions`

- Add a command to read `version`: `mddj read version`
- Convert implicit build usage and metadata extraction to use `build.util`
- Support disabling isolated builds via `MDDJ_BUILD_ISOLATION=0` env var
- Add `wheel` as a dependency, and remove `importlib_metadata`
- Add `tomli` as a dependency on pythons below Python 3.11
- Add a command for writing version updates, `mddj write version`
- Config is now supported in the `tool.mddj` table of `pyproject.toml`. Only
one config value is supported, `write_version`

- Support invocation using `python -m`