Add Docs Check to Pull Request CI

[adambkaplan]

Issue

The community has decided to keep reference documentation in the same tree as code to facilitate high quality contributions.
To publish this documentation, the website repo will utilize a sync script that copy docs markdown from the code repositories to the website repo, which then generates the static HTML.
In order for the website to render correctly, "front matter" metadata needs to be embedded in the markdown stored in code repositories.

Proposed Solution

Add a "docs" GitHub action in shipwright-io/build (and future repositories) which checks out the website code, runs the sync, and then has hugo generate the static content.
Failures here will need to have clear messaging so contributors know what went wrong and how to fix it.

Hopefully we will catch 90% of bugs that would cause the Netlify deployment to fail from synced content.

Notes

Depends on shipwright-io/website#29

Originally posted by @adambkaplan in shipwright-io/website#27 (comment)

[qu1queee]

@adambkaplan from grooming session, can you provide the status of this one pls?

[adambkaplan]

This still depends on the website issue, which is currently open.

[qu1queee]

@adambkaplan is this something that is already done?

[qu1queee]

from grooming:

• do we need to start versioning on the docs in the website?

[adambkaplan]

Website issue is still open.

do we need to start versioning on the docs in the website?

Since we are still in an alpha phase, I don't think versioned docs is necessary. I think once we have a more stable API (v1beta1) then versioned docs make sense.