Add Prerender Buddy extension to workflow tools

[kopachlager]

Add Prerender Buddy extension for crawler-readability checks to workflow tools.

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[kopachlager]

Following up now that the Google CLA and repository checks are passing. The extension remains published and maintained, and this listing change is ready for review. Please let me know if any adjustment is needed.

[paulirish]

Closing this out. Per the Awesome Manifesto, this list is a strict curation of standout, open-source tools—not a directory of everything in the space. I'm passing on submissions that are closed-source, overlap heavily with established tools, or haven't yet seen strong community adoption.

I know it sucks to get a curt rejection after putting a PR together, and I'm sorry, but this is my call as maintainer to keep the list small and high-signal. Sorry, and thanks for understanding.