RFR: Section on project maintenance [v6]

[Iris Clark]

On Tue, 20 Dec 2022 12:57:29 GMT, Jesper Wilhelmsson <jwilhelm at openjdk.org> wrote:

>> * New section on project maintenance
>> * New infographics on push/defer during rampdown
>> * Moved JDK Release Process section to follow the Release Note section
>> * Minor fixes
>
> Jesper Wilhelmsson has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Minor clarification around jtreg.

Marked as reviewed by iris (Reviewer).

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PR: https://git.openjdk.org/guide/pull/92