chore: add GH Action, on Snyk PRs commit yarn.lock

[jordanh]

Description

Had a couple of minutes for a little palette cleanser. Decided to create this action.

If the PR title include [snyk] (case-insensitive), check out the PR branch, run yarn install, and then commit the resulting lock file and push the branch.

Testing scenarios

• Close a snyk PR and reopen it

Final checklist

• I checked the code review guidelines
• I have added Metrics Representative as reviewer(s) if my PR invovles metrics/data/analytics related changes
• I have performed a self-review of my code, the same way I'd do it for any other team member
• I have tested all cases I listed in the testing scenarios and I haven't found any issues or regressions
• Whenever I took a non-obvious choice I added a comment explaining why I did it this way
• I added the label Skip Maintainer Review Indicating the PR only requires reviewer review and can be merged right after it's approved if the PR introduces only minor changes, does not contain any architectural changes or does not introduce any new patterns and I think one review is sufficient'
• PR title is human readable and could be used in changelog

[jordanh]

We're going to merge it 🔒 , and see what happens 😬