RFR: Added section for newcomers [v4]

[Magnus Ihse Bursie]

On Wed, 18 Nov 2020 22:25:23 GMT, Jesper Wilhelmsson <jwilhelm at openjdk.org> wrote:

>> Added a section to the introduction to set the expectations for new developers in the OpenJDK.
>> 
>> I also moved the mail list section up since it's also relevant in this context and should (imho) be the first thing to learn about when thinking about joining the community.
>
> Jesper Wilhelmsson has updated the pull request incrementally with one additional commit since the last revision:
> 
>   why is my change rejected?

Marked as reviewed by ihse (no project role).

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PR: https://git.openjdk.java.net/guide/pull/38