RFR: 7903271: Add sample of libzstd [v3]

[Mike Duigou]

On Tue, 30 Aug 2022 13:49:24 GMT, Per Minborg <duke at openjdk.org> wrote:

>> This PR adds a sample using `libzstd`, a high-performance compression library.
>
> 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!

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