Improve documentation for generating GraalVM native image with Gradle build tool

[bhavikp19]

I think that picocli documentation around generating GraalVM native image with gradle build tool can be improved a lot. Here are couple of things that I have in mind :

1. In this section of documentation https://picocli.info/#_how_do_i_create_a_native_image_for_my_application we ask users to check out gradle-graal gradle plugin but this plugin is not actively maintained. This was last released in June 2022 and lot of the recent commits are from Excavator bot. I think we should instead direct users to use the official GraalVM gradle plugin.
2. In this section of documentation https://picocli.info/#_where_can_i_get_more_details we link to demo gradle project where we can improve on the github action https://github.com/remkop/picocli-native-image-demo/blob/master/.github/workflows/gradle.yml. Official GraalVM gradle plugin now makes it very easy to generate native images on Linux, MacOS and specially Windows. Documentation can be found here : https://graalvm.github.io/native-build-tools/latest/gradle-plugin.html.

If you agree with these suggestions then I am happy to work on and submit the PR for above changes.

[remkop]

Yes please! Thank you!

[bhavikp19]

For 1. above, do I edit the .adoc file or the .html file?

For 2. I should raise the PR directly for https://github.com/remkop/picocli-native-image-demo/tree/master repository?

[remkop]

For 1. above, do I edit the .adoc file or the .html file?

Only the .adoc files is fine. The HTML files are generated from the ADOC files upon release.

For 2. I should raise the PR directly for https://github.com/remkop/picocli-native-image-demo/tree/master repository?

Yes that is fine.

Thank you!

[bhavikp19]

For 2. above I have raised the PR : remkop/picocli-native-image-demo#5

[bhavikp19]

For 1. above I have raised the PR : #2080

[remkop]

Both are now merged. Thank you for the contribution!