Allow @ShowkaseComposable as annotation for annotation class

[ln-12]

Hey, I have a feature request which is kind of related to #233.

The @Preview annotation can be used for functions and other annotation classed (see here). @ShowkaseComposable can only be used for functions. I would like to do the following:

// some other annotations
@ShowkaseComposable
annotation class DefaultPreview

This is already possible with @Preview. Do you see any issues when allowing @ShowkaseComposable on annotation classes to achieve that? I think the only thing needed for that would be to add AnnotationTarget.ANNOTATION_CLASS here.

[Vinay Gaba]

@oas004 Any chance you could add the same functionality to ShowkaseComposable as well? Trying to remember why you didn't add this in the original PR's itself?

[Odin Asbjørnsen]

Hey, I think I just might have forgotten to add that as well in the initial PRs. I think that should be possible, but I'm not sure that it is as easy as just adding AnnotationTarget.ANNOTATION_CLASS. I can try to look into it this weekend if that is okay? :)

Do you think it would make sense to add the repeatable pattern as well to this annotation? So that this is possible?

@ShokaseComposable
@ShowkaseComposable
annotation class DefaultPreview

and

@ShokaseComposable
@ShowkaseComposable
@Composable
fun SomePreview()