Danger shouldnt require PR link: Automation appends link

[bruno-garcia]

Danger should validate an entry exists in the changelog but not require the PR number to be added.

Danger when running could add the PR number (i.e: getsentry/sentry-unity#123) to the changelog entry.

This way our workflow can change from:

• pushing a branch
• opening a PR
• getting nagged by danger for a missing changelog entry
• add changelog with PR number

To:

• pushing a branch with a changelog entry missing the PR number
• opening a PR (or gh pr create --fill)

An automation that runs once the branch is merged to main will append the PR number to the line (and avoid running CI on anything since only CHANGELOG will change)

An evolution from: getsentry/sentry-unity#155

[bruno-garcia]

Adding the commit to main would avoid pushing to the PR but would pollute the main branch. So best to change the danger file and just push to the PR as we do with code formatting