chore: Introduce release notes formatting + preview release action

[olivermrbl]

What

• Add changelog formatting file to automate pull request categorization in release notes*
• Add action to trigger preview releases
• Remove unused staging deployment action

Add changelog formatting file to automate pull request categorization in release notes

In order for this work, we need to be more strict about our labels usage. More specifically, we need to add one of the four different labels noted in the release.yml file. The labels should be self-explanatory. If your PR introduces both features and bugs, you should choose the label based on importance of the changes.

[changeset-bot]

⚠️ No Changeset found

Latest commit: e1548a8

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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[vercel]

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Name	Status	Preview	Comments	Updated (UTC)
medusa-dashboard	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	May 6, 2024 0:10am

3 Ignored Deployments

Name	Status	Preview	Comments	Updated (UTC)
api-reference	⬜️ Ignored (Inspect)			May 6, 2024 0:10am
docs-ui	⬜️ Ignored (Inspect)			May 6, 2024 0:10am
medusa-docs	⬜️ Ignored (Inspect)	Visit Preview		May 6, 2024 0:10am

[adrien2p]

LGTM, one small suggestion