add ci check that auto comments preview link

[mirnawong1]

this pr adds a ci that auto-comments the staging link using the branch-name to make it easier for the author, reviewer, and any other viewer.

test pr: #6098

outstanding:

• i'd like to change the github action yaml so that it picks up frontmatter id first and then file name since sometimes we use a diff id
• i'd like to add a time delay os it posts after or around went vercel deploys
• how will this interact with open source contributions w/o vercel access (will checks fair or output incorrect preview link)

[vercel]

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Name	Status	Preview	Updated (UTC)
docs-getdbt-com	✅ Ready (Inspect)	Visit Preview	Oct 15, 2024 9:14am

[JKarlavige]

Hey @mirnawong1, looking into this now. Do you have a way for me to test this within this PR?

[mirnawong1]

hey @JKarlavige ! i created a test pr #6098 to test it. so if you made changes to a file, it should post the link 🤞

[JKarlavige]

@mirnawong1 this is great! Verified in PR #6098 a new preview link was added to the description after pushing an update. The preview URL added to the description was the correct page.

Awesome work with this, this is a great value add to these PRs!!