chore: automate PR from dev to main

[susanshi]

What would you like to be added?

We have a workflow at https://github.com/deislabs/ratify/blob/staging/.github/workflows/pr-to-main.yml, we need to create a Access Token so this workflow could create PR automatically.

Anything else you would like to add?

No response

Are you willing to submit PRs to contribute to this feature?

• [ ] Yes, I am willing to implement it.