Add ThemeKit.gitlab-ci.yml to jh directory

What does this MR do and why?

Upstream added ThemeKit.gitlab-ci.yml https://gitlab.com/gitlab-org/gitlab/-/commit/fbf1eb5f6c36c36e1b8a25430fd19ab6f781c3b1 and we don't have this file, so I add it to jh directory.

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