Add support for clojure projects using leiningen

Thanks for stopping by to let us know something could be better!

**Is your feature request related to a problem? Please describe.**

Clojure projects with Leiningen are not currently supported, but could be supported.

**Describe the solution you'd like**

I'd like to be able to use release-please with Clojure

**Describe alternatives you've considered**

- Not using release-please
- Writing a plugin for release-please