RFR: Add Premain EA link, Premain JEP links, link to training run doc

[Dan Heidinga]

On Tue, 17 Sep 2024 02:29:15 GMT, John R Rose <jrose at openjdk.org> wrote:

> Some adds to the index page:
> 
>  - premain JEP and EA links
>  - link to Dan's doc about training runs
> 
> One thing that baffled me a bit is the `<br/>` elements in the markdown.  These seem to be either hand-inserted as an attempt to do line length control, or else they are artifacts of an old cut-and-paste. Do we really want them?  If so, can we put in a comment in the markdown that says how to maintain them, please?

looks good to me

-------------

Marked as reviewed by heidinga (Committer).

PR Review: https://git.openjdk.org/leyden-docs/pull/4#pullrequestreview-2309786718