RFR: New text about mailing lists [v3]

[Jesper Wilhelmsson]

> I'm wondering if subscription recommendations should be made for those new to OpenJDK?  Whenever I'm asked, my response
> is usually announce, discuss, and the "-dev" list(s?) covering the explicit area of interest.
> 
> Random note:  Per the Bylaws, OpenJDK mailing list subscribers are defined as "Participants"
> (https://openjdk.java.net/bylaws#participant).

Thanks for the review! I added the recommendation as per your suggestion.

Thanks,
/Jesper