Expose KT rules to be used in stardoc generation of custom rules

[tharakadesilva]

I am writing my own set of rules on top of rules_kotlin, but my stardoc generation is failing due to the "limited visibility" in rules_kotlin.

There is an open issue https://github.com/bazelbuild/stardoc/issues/93 to add a better fix for this.

Till then, would it be possible to expose a bzl_library similar to https://github.com/bazelbuild/rules_jvm_external/pull/527?