Add ability for socket REPL to pick up the port from a file

[cursive-ghost]

Reported by @finalfantasia in Slack:

Can you please add the ability for Cursive to pick up a socket REPL port from a file in the Edit Configuration Settings window? Similar to the “Use port from nREPL file” option for nREPL or a more generalized version of it? I know there’s not a similar standard for socket REPL yet but this is going to be really handy with tools that provide such files (e.g., shadow-cljs writes the socket REPL port to a file named .shadow-cljs/socket-repl.port).