Add Stage to Main workflow

[Brandon32]

To automate our process and to follow suit with Milo we should implement a simplified version of merge-to-main.

We should also consider adding a simplified merge-to-stage workflow to streamline merging and automate Release PRs.

See:

• https://github.com/adobecom/milo/blob/stage/.github/workflows/merge-to-main.js
• https://github.com/adobecom/milo/blob/stage/.github/workflows/merge-to-stage.js