Support documentation validation

[MahdiBM]

Please summarize your feature request

Support documentation validation

Describe the functionality you're seeking in more detail

See
https://github.com/swiftlang/github-workflows/blob/717bc4bb20cc278aaaa031bde960c392d65b8f4e/.github/workflows/soundness.yml#L14
https://github.com/swiftlang/github-workflows/blob/717bc4bb20cc278aaaa031bde960c392d65b8f4e/.github/workflows/scripts/check-docs.sh

Have you considered any alternatives?

No response

[gwynne]

I want this. Would worry about running afoul of swiftlang/github-workflows#166 though.

[0xTim]

I would say we should only build on Linux for documentation.

Are we able to call the Swiftlang workflow from ours?

[gwynne]

Should be able to, it's just another level of reusable workflow, they can nest (though there's a limit to how deep). I don't see anything that would make it unusable. I don't remember what Swift version the fix for the "sameShape" constraint problem went into, though... without that fix some of our docs don't build properly.