RFR: Add jextract guide [v6]

[Jorn Vernee]

On Mon, 15 Apr 2024 15:37:57 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> I gave this a try in the latest version. Still not sure which one is better, but I don't mind either way. I put all the sections after the examples in an 'Advanced' section as well.
>
> I personally like the new changes a lot! I find the "running jextract" section very informative, providing all the major info w/o overstaying its welcome. Also it points to several other sections in the doc, so it acts a bit as a mental map, which is good.
> 
> I have some reservation about "unsupported features" being down in "Advanced" - should that be the last section in "Using jextract bindings" instead? (e.g. first we show what works, and then if the reader was expecting something else, we have a section for that too). Or, maybe pull it more "up front". Right now it seems kind of buried in other stuff, even thought it seems generally useful.

Ok, I'll keep it like this then.

I'll move the unsupported feature to the end of the 'using' section.

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PR Review Comment: https://git.openjdk.org/jextract/pull/231#discussion_r1566019600