docs(author-profile): add block README

[rbcorrales]

All Submissions:

• Have you followed the Newspack Contributing guideline?
• Does your code follow the WordPress' coding standards and VIP Go coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Adds a developer-facing README for the Author Profile block.

Closes NPPD-1220.

How to test the changes in this Pull Request:

1. Open src/blocks/author-profile/README.md and verify the content renders correctly on GitHub.
2. Confirm that relative links (to templates, other blocks within the repo) resolve correctly.
3. Confirm that absolute GitHub links (to newspack-plugin blocks) resolve correctly.

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully ran tests with your changes locally?

[Copilot]

Pull request overview

Adds developer-facing documentation for the author-profile Gutenberg block, describing operating modes, rendering behavior, attributes, bindings, and editor UX.

Changes:

• Introduces src/blocks/author-profile/README.md explaining the Author Profile block’s modes and rendering strategy.
• Documents block attributes and block bindings keys.
• Adds “Related” links to companion blocks/templates.

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[rbcorrales]

All flagged items reference code (variations, templates, variation attribute, variation picker UI) that exists on the feature branch in #2302. This docs PR is meant to land after that PR merges to trunk. Resolving all threads as false positives.

[laurelfulford]

This looks good @rbcorrales! I just flagged one line that may need to be clipped depending on how the feedback in the variation picker PR is handled, but I don't think that's a blocker since this is correct for how it works right now, and the text can be changed after the behaviour's changed :)

[github-actions]

Hey @rbcorrales, good job getting this PR merged! 🎉

Now, the needs-changelog label has been added to it.

Please check if this PR needs to be included in the "Upcoming Changes" and "Release Notes" doc. If it doesn't, simply remove the label.

If it does, please add an entry to our shared document, with screenshots and testing instructions if applicable, then remove the label.

Thank you! ❤️