RFR: JDK-8298405: Support Markdown in Documentation Comments

[Erik Joelsson]

On Thu, 26 Oct 2023 23:29:00 GMT, Jonathan Gibbons <jjg at openjdk.org> wrote:

> Please review a patch to add support for Markdown syntax in documentation comments, as described in the associated JEP.
> 
> Notable features:
> 
> * support for `///` documentation comments in `JavaTokenizer`
> * new module `jdk.internal.md` -- a private copy of the `commonmark-java` library
> * updates to `DocCommentParser` to treat `///` comments as Markdown
> * updates to the standard doclet to render Markdown comments in HTML

Build change looks trivially ok.

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PR Review: https://git.openjdk.org/jdk/pull/16388#pullrequestreview-1716568732