Add a bit about socket REPLs

[mfikes]

This page https://clojurescript.org/reference/repl-and-main can be updated for Socket REPLs (a bit like, or referring to https://clojure.org/reference/repl_and_main#_launching_a_socket_server)

In particular, it can explain how, with Clojure 1.10, you can

clj -J-Dclojure.server.repl='{:port 5555 :accept cljs.server.browser/repl}'

Replacing cljs.server.browser/repl with any of the other shipping REPLs, and then connecting to port 5555 to launch the REPL.

[swannodette]

It's definitely a gaping hole wrt. REPL docs