RFR: JDK-8295914: Add a header to generated HTML files in specs

[Iris Clark]

On Thu, 27 Oct 2022 20:50:04 GMT, Jonathan Gibbons <jjg at openjdk.org> wrote:

> Please review some updates to the parts of the build system related to building the documentation.

Your changes look good!  Can't wait to see this in a promotion.

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Marked as reviewed by iris (Reviewer).

PR: https://git.openjdk.org/jdk/pull/10891