Run other doctest formats if dependencies are present

There are several formats for doctests:

• "=>" followed by a form with the results on the next line (what testdoc calls "REPL style" )
• A form followed by a "=>" with results ("Code-first style")
• A comment form with "=>" with results (I guess we could call this rich comments style)

If we don't want to extend the parser to accept all these different types, we could look for libraries that provide them on the classpath and use those libraries to collect those tests. If these already support clojure.test, I think it would be quite easy.

I'm a little concerned this could lead to confusion, but projects generally shouldn't have multiple doctest formats or libraries present (and if they do, they're already in a confusing situation), unless they're migrating.

Start by reviewing the existing doctest parser and how Kaocha-doctest discovers tests on the classpath. Investigate libraries supporting REPL-style, code-first, or rich-comments doctests and whether they integrate with clojure.test. Done means agreeing on supported formats or libraries and defining tests for the selected behavior.