RFR: 8357000: Write overview documentation for start of release changes [v4]

[Iris Clark]

On Tue, 3 Jun 2025 04:43:59 GMT, Joe Darcy <darcy at openjdk.org> wrote:

>> First attempt to populate "supplementary docs" with a discussion of the start of release changes. For reference on the idea of supplementary docs, see the thread
>> 
>> "Where to put supplementary docs?"
>> https://mail.openjdk.org/pipermail/jdk-dev/2025-April/009975.html
>
> Joe Darcy has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Update description of start of release changes.
>  - Move file up a directory.

Marked as reviewed by iris (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/25317#pullrequestreview-2893262736