RFR: 7903635: jextract README page is obsolete

[Jorn Vernee]

On Wed, 17 Jan 2024 12:43:49 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> This PR updates the README with code snippets that are compatible with the new generated code.
> When zooming in on what jextract generates to bind a function, instead of aiming for 100% fidelity, I tried to doctor the code a little, to make it a bit clearer, and avoid details such as holder classes and tracing support which, I think are too low-level at this stage.

Marked as reviewed by jvernee (Committer).

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

PR Review: https://git.openjdk.org/jextract/pull/182#pullrequestreview-1827273711