Add 'scripts/github/update-gh-pages.sh' for updating gh-pages branch.
This new script intended for github actions integration and builds the
html documentation from the currently checked-out commit and updates the
corresponding version subfolder in the gh-pages branch. The version is
taken from GITHUB_REF environment variable and defaults to 'master' if
the env var is empty. For testing purposes or manual updates the
subfolder can also be given directly as a command line argument.
Add 'scripts/test-infra/build-gh-pages.sh' for verifying that site
(gh-pages) builds successfully. This is intended for integration with
kubernetes test-infra.
Finally, add Github workflow for updating gh-pages. This job is run on
master and release branches plus all tags starting with letter 'v'.
(cherry picked from commit c5beeffb6a)
