Add a new backend - Clojure's tablecloth

[kirahowe]

Hi there! This is a really cool project, thanks for keeping it going. Would the maintainers be open to accepting a solution using Clojure's tablecloth? It's the main dataframe/datatable manipulation library in our toolkit, entirely free and open source. I'm active in the Clojure-for-data-science community and would happily contribute a PR with the Clojure setup and solutions, but wanted to check first whether it's likely to be accepted. If so, are there any specific guidelines or requirements for contributing a new language (Clojure runs on the JVM).