[#495] add clojure.java.browse/browse-url

[borkdude]

Fixes #495.
cc @lread

One issue remains to be fixed on Windows:

C:\Users\borkdude\Downloads>bb -e "(require '[clojure.java.browse :refer [browse-url]]) (browse-url \"https://babashka.org\")"
java.io.IOException: Cannot run program "start": CreateProcess error=2, The system cannot find the file specified [at line 1, column 54]

This seems to work:

> bb -e "(require '[clojure.java.shell :refer [sh]]) (sh \"cmd.exe\" \"/C\" \"start\" \"https://babashka.org\")"
{:exit 0, :out "", :err ""}