feat: add GITLAB_COMMENT_TYPE env variable to use discussions or notes

[QuiiBz]

This PR adds a new COMMENT_TYPE environment variable, to control the type of comment created when using changesets-gitlab comment:

• discussion creates a new discussion (thread). This is the default
• note creates a note (comment)

This is useful when a GitLab repo requires all threads to be resolved before merging an MR. We can instead use this new note COMMENT_TYPE which won't block merging.

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[changeset-bot]

🦋 Changeset detected

Latest commit: f0b4ceb

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
changesets-gitlab	Minor

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[JounQin]

This is useful when a GitLab repo requires all threads to be resolved before merging an MR.

Just curious, why not just resolve the thread if you want to merge?

[QuiiBz]

Just curious, why not just resolve the thread if you want to merge?

It creates an extra step that isn't needed, and makes it impossible to auto-merge MR from bots (e.g renovate).

[JounQin]

It creates an extra step that isn't needed, and makes it impossible to auto-merge MR from bots (e.g renovate).

Thanks for explain! I didn't use auto-merge MR from bots in GitLab.

I think this PR is acceptable.