introduce //USE notion

[maxandersen]

originally for jbang I was thinking we should allow //DEPS log4j,xchart as a shorthand for adding the "sensible default set " of dependencies for a java app.

I never did it as it felt somewhat "wrong" to mix this into the raw dependency feature.

Recently I played around with juypter kernels and noticed the kotlin kernel has a %use syntax https://github.com/Kotlin/kotlin-jupyter#supported-libraries.

They have something akin to jbang-catalog and our --source notion which in context of jshell lets you set things up.

Noteworthy is that they have separation of imports and code - but I would say we could handle that by just stripping out ^import .* lines from our sources and use it.

Idea is that you would be able to do //USE faker@jbangdev and we probably should ensure it should be possible to just use //USE faker.

They do also allow %use faker(5.5) where the parameter is used as explicit value for $v in the include. Used to handle custom versions.

Similar they have %useLatestDescriptors which afaics defaults $v to be LATEST.

The usecase for all this is simply to make it super easy to get started with scripting and not having to think/remember much.

With tooling it would "just work" as the sideffect would just be //DEPS in the background for .java and for .jsh we would add imports and default init code.