RFR: 7903271: Add sample of libzstd [v3]

[Per Minborg]

On Tue, 30 Aug 2022 17:04:54 GMT, Mike Duigou <mduigou at openjdk.org> wrote:

>> Per Minborg has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Update copyright year
>
> Thank you for contributing this example!

Thanks @bondolo for your feedback. Please review https://github.com/openjdk/jextract/pull/68 where I have incorporated your suggestions above.

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PR: https://git.openjdk.org/jextract/pull/66