RFR: Section on backporting [v8]

[Iris Clark]

On Wed, 22 Dec 2021 17:08:54 GMT, Jesper Wilhelmsson <jwilhelm at openjdk.org> wrote:

>> Guidance on backporting.
>> Also moved "Backing out a change" to the testing section where I believe it fits better. This section is unchanged.
>
> Jesper Wilhelmsson has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 10 commits:
> 
>  - Merge branch 'master' of github.com:openjdk/guide into backport
>  - Fixes after review
>  - Update src/index.md
>    
>    Co-authored-by: Andrew Haley <aph-open at littlepinkcloud.com>
>  - Updated todo-list
>  - Merge branch 'backport' of github.com:JesperIRL/guide into backport
>  - Update src/index.md
>    
>    Co-authored-by: Magnus Ihse Bursie <mag at icus.se>
>  - Update src/index.md
>    
>    Co-authored-by: Magnus Ihse Bursie <mag at icus.se>
>  - jdk<release>u-fix-yes
>  - Fixes after reviews
>  - Section on backporting

Marked as reviewed by iris (Reviewer).

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PR: https://git.openjdk.java.net/guide/pull/66