feat(config): add field and value matchers to the commit parser

[dpecos]

Description

This PR introduces the capability of grouping commits by attributes of the commit, i.e. author.name or author.email.

Motivation and Context

This changeset should cover the scenario described in #194.

The reporter of that issue wanted to create a new group based gathering the commits for a specific author name:

 { author.name = "Renovate Bot", group = "Dependency Updates"},

How Has This Been Tested?

In order to test it works, I've modified the cliff.toml file in this project to include a new group like this:

commit_parsers = [
  { field = "author.name", pattern="dependabot\\[bot\\]", group = "Dependency Updates"},
  ...

which generates the following new group:

### Dependency Updates

- *(deps)* Bump regex from 1.9.6 to 1.10.0 ([#308](https://github.com/orhun/git-cliff/issues/308)) - ([a6a890a](https://github.com/orhun/git-cliff/commit/a6a890ac4f0051518b4b4c0d65a5ce83ae0de1c8))
- *(deps)* Bump toml from 0.8.1 to 0.8.2 ([#306](https://github.com/orhun/git-cliff/issues/306)) - ([8422096](https://github.com/orhun/git-cliff/commit/8422096549320604643cda9baab4190a5de272fb))
- *(deps)* Bump regex from 1.9.5 to 1.9.6 ([#305](https://github.com/orhun/git-cliff/issues/305)) - ([e263163](https://github.com/orhun/git-cliff/commit/e2631639bf0438fb8f67e3b99c27354fd7409f57))

Screenshots / Logs (if applicable)

Types of Changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (no code change)
• Refactor (refactoring production code)
• Other

Checklist:

• My code follows the code style of this project.
• I have updated the documentation accordingly.
• I have formatted the code with rustfmt.
• I checked the lints with clippy.
• I have added tests to cover my changes.
• All new and existing tests passed.

[welcome]

Thanks for opening this pull request! Please check out our contributing guidelines! ⛰️

[codecov-commenter]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Files	Coverage Δ
git-cliff-core/src/changelog.rs	55.67% <ø> (ø)
git-cliff-core/src/config.rs	41.67% <ø> (ø)
git-cliff-core/src/commit.rs	90.67% <60.00%> (-4.88%)	⬇️

📢 Thoughts on this report? Let us know!.

[orhun]

Thanks a lot for your contribution! Just had some suggestions for improving the code.

[orhun]

Also, can you resolve the conflicts with main?

[dpecos]

Suggestions applied (btw, I really like the refactor for the big switch case I had) and changes from main pulled :-)

[orhun]

LGTM, thanks for your contribution!

It was really fun working with you at the EuroRust workshop @dpecos! Wish to see you in the future events/open source projects. ❤️

[welcome]

Congrats on merging your first pull request! ⛰️