feat: add preview static pages action

[haochunchang]

PR Checklist

• Read the Contributing documentation.
• Read the Code of conduct documentation.
• Name your Pull Request title clearly, concisely, and prefixed with the name of the primarily affected package you changed according to Good commit messages (such as memory: add interfaces for X, Y or util: add whizzbang helpers).
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. Fixes #123).
• Describes the source of new concepts.
• References existing implementations as appropriate.
• Contains test coverage for new functions.
• Passes all golangci-lint checks.

• New GitHub action source: https://github.com/marketplace/actions/preview-pages

[tmc]

@haochunchang what's needed to get this to a review-ready state?

[haochunchang]

@haochunchang what's needed to get this to a review-ready state?

I was hoping I can see a doc site preview in one of those checks.

[haochunchang]

The Github action to be introduced: https://github.com/marketplace/actions/preview-pages