RFR: Add section on pre-built binaries to README

[Athijegannathan Sundararajan]

On Fri, 7 Oct 2022 11:43:36 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

> I've added a short section on where to find the pre-built binaries. I think building jextract is less important than the information on usage if people can get binaries, so I've moved the section on building and testing to the bottom.

Looks good

README.md line 7:

> 5: ### Getting jextract
> 6: 
> 7: Pre-built binaries for jextract are peridodically released here: https://jdk.java.net/jextract/. These binaries are built from the `master` branch of this repo, and generally target the foreign memory access and function API in the latest mainline JDK (for which binaries can also be found on [jdk.java.net](https://jdk.java.net)).

could  https://jdk.java.net/jextract/ be a link?

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Marked as reviewed by sundar (Committer).

PR: https://git.openjdk.org/jextract/pull/84