RFR: Section on project maintenance [v3]

[David Holmes]

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

src/guide/project-maintenance.md line 62:

> 60: ~~~
> 61: 
> 62: These commands will remove the temporary branch that we created to perform the merge.

The github UI has a button to delete the branch after you have integrated the PR.

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