feat: add Conventional Changelog provider

[jonahsnider]

Adds a Conventional Changelog provider, which is used by a bunch of tools (ex. Release Please)

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[HiDeoo]

Thanks for the contribution.

I did not review the code yet but I have some high-level questions about Conventional Changelog:

• They don't have some kind of spec or something similar regarding the output format? I couldn't really find anything in the docs (I guess it would make sense if anything is managed using presets and each preset would have its own output format?).
• I see that multiple presets are available by default, I guess we would need to support all of them using a preset option?

[jonahsnider]

They don't have some kind of spec or something similar regarding the output format?

Correct, no formal output spec, just whatever the official providers emit as a reference

I see that multiple presets are available by default, I guess we would need to support all of them using a preset option?

Both of the official presets use the same heading format, so in this case we don't need any kind of special parsing logic for them

[HiDeoo]

Both of the official presets use the same heading format, so in this case we don't need any kind of special parsing logic for them

According to the doc, I think there may be a difference in version heading level?

Conventional Commits preset	Angular Preset

[jonahsnider]

Ah yeah, the headings are different depending on output format but since we define versionHeadingLevel: [1, 2, 3] it handles both variants

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[HiDeoo]

Ah yeah, the headings are different depending on output format but since we define versionHeadingLevel: [1, 2, 3] it handles both variants

I see, thanks for the clarification and taking the time to go with me through the details.

This looks great to me. I pushed a small refactor unifying versionHeadingLevel and isVersionHeading to a single function as it felt a bit more natural to me to only have one place to define the logic for identifying version headings.

Thanks for the contribution 🙌