This PR intended to resolve #9831 issue.

Currently snapshots are not synced to latest snapshot tests results.
This PR add snapshot,yml workflow to update snapshots.
And run ci.yml if snapshots are updated.

How to run snapshot update workflow

First of all. This PR must be merged to main branch to run workflow.

After PR is merged.
It can run workflow via GitHub Action Web UI.

It can also run workflow by using gh command.

gh workflow run snapshot.yml --repo dotnet/docfx --ref test-branch -f dryrun=true

How to test snapshot workflow

1. Ensure this PR is merged to main branch.
2. Create test branch (e.g. test-branch) and push to GitHub.
3. Run snapshot workflow with dryrun=false setting
4. Confirm snapshot is updated by workflow. And cy.yml is executed.

If it's confirmed to works as expected.
Please try to update main branch snapshot.