Missing ElementType.ANNOTATION_TYPE in Tracings annotations

[ajtuss]

Hey,

I would like to create an annotation to group a few others, but just realized that none of the tracings annotations hasn’t ElementType.ANNOTATION_TYPE (eg. @SpanTag, @ContinueSpan...)
Is this intentional, or can I do a PR to add it?

Here is an example what I want to achive:

@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Target(value = { ElementType.PARAMETER })
@SpanTag("foo") //non compile here
@PathVariable("foo")
public @interface Foo {
}

Regards.

[graemerocher]

Sounds reasonable, PRs welcome!