RFR: Section on project maintenance [v3]

[Iris Clark]

On Wed, 21 Sep 2022 20:15:00 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:
> 
>   Update after Ludvig's review

Marked as reviewed by iris (Reviewer).

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

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