Add optional headers param for logout redirect

[coryagami]

WHY are these changes introduced?

This allows for passing Set-Cookie headers to the logout redirect, allowing users the possibility of clearing certain cookies (like the cart) on logout.

This is being used in our app to allow multiple users to share a login device without persisting carts across users.

WHAT is this pull request doing?

Passing through an optional headers param to the logout redirect call.

HOW to test your changes?

Added a new test to customer.test.ts to test this functionality.

Checklist

• [x] I've read the Contributing Guidelines
• [x] I've considered possible cross-platform impacts (Mac, Linux, Windows)
• [x] I've added a changeset if this PR contains user-facing or noteworthy changes
• [x] I've added tests to cover my changes
• [x] I've added or updated the documentation

[coryagami]

Thanks for the contribution. Please include a changeset by running npm run changeset - choose patch update

Thanks @wizardlyhel! I added a patch changeset. For future reference, do we always need a changeset for the workflow to succeed anytime we make any changes in src/ ?

[wizardlyhel]

changeset is a must - It's how we can automatically attribute your contributions in our changelog CI workflow is something we have to evaluate your code first before approving it to run