Feature
* feat: support toml files for version declaration (307)
This introduce a new `version_toml` configuration property that behaves
like `version_pattern` and `version_variable`.
For poetry support, user should now set `version_toml = pyproject.toml:tool.poetry.version`.
This introduce an ABC class, `VersionDeclaration`, that
can be implemented to add other version declarations with ease.
`toml` dependency has been replaced by `tomlkit`, as this is used
the library used by poetry to generate the `pyproject.toml` file, and
is able to keep the ordering of data defined in the file.
Existing `VersionPattern` class has been renamed to
`PatternVersionDeclaration` and now implements `VersionDeclaration`.
`load_version_patterns()` function has been renamed to
`load_version_declarations()` and now return a list of
`VersionDeclaration` implementations.
Close 245
Close 275 ([`9b62a7e`](https://github.com/python-semantic-release/python-semantic-release/commit/9b62a7e377378667e716384684a47cdf392093fa))