RFR: Add jextract guide [v4]

[Maurizio Cimadamore]

On Wed, 10 Apr 2024 14:13:37 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

>> Add a comprehensive jextract guide under a new `doc/` folder.
>> 
>> This is meant as a comprehensive guide about the features of jextract and the code that it generates (including both examples from header files, the code that jextract generates, and corresponding Java user code). This is a first cut, and I'm anticipating quite a bit of comments.
>> 
>> Some sections of the readme have been moved to the guide (with minor edits here and there), and replaced by a link in the readme.
>
> Jorn Vernee has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Split sentence

Marked as reviewed by mcimadamore (Reviewer).

Great job! The guide reads great, and was long overdue :-)

doc/GUIDE.md line 407:

> 405: ### Function Pointers
> 406: 
> 407: Jextract will generate a separate class for each function pointer type found in the header

Suggestion:

Jextract generates a separate class for each function pointer type found in the header

doc/GUIDE.md line 505:

> 503: (such as struct fields or global variables):
> 504: 
> 505: ```c

thanks!

-------------

PR Review: https://git.openjdk.org/jextract/pull/231#pullrequestreview-1991864013
PR Comment: https://git.openjdk.org/jextract/pull/231#issuecomment-2047709012
PR Review Comment: https://git.openjdk.org/jextract/pull/231#discussion_r1559545650
PR Review Comment: https://git.openjdk.org/jextract/pull/231#discussion_r1559547444