RFR: 7903866: apidiff: add an example to the doc [v3]

[duke]

On Sun, 20 Oct 2024 13:33:40 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> It's an example, for example. We need more.
>
> Andrew Haley has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add an example

@theRealAph 
Your change (at version 249c1bb755dcb61ff4063d991e2b31a6bf8a9719) is now ready to be sponsored by a Committer.

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PR Comment: https://git.openjdk.org/apidiff/pull/26#issuecomment-2431585484