lucky dev: When Ctrl+C is pressed, wait for the child process to hand…

…le the signal and finish - rather than us immediately exiting and leaving it to log shutting down messages from the background (luckyframework#572)

* lucky dev: When Ctrl+C is pressed, wait for the child process to handle the signal and finish - rather than us immediately exiting and leaving it to log shutting down messages from the background

Resolves luckyframework#570. I've just used the approach I suggested there.

I wasn't sure how/if to write a spec for this, so I haven't. Is that acceptable?

To test it manually, I ran this from my app directory before and after the change to verify the behaviour:

```bash
$ crystal run ~/Projects/lucky_cli/src/lucky.cr -- dev
```

* Update src/lucky_cli/process_runner.cr

* oops. formatted

Co-authored-by: Jeremy Woertink <jeremywoertink@gmail.com>

src/lucky_cli/process_runner.cr

@@ -31,6 +31,10 @@ module LuckyCli
     end
 
     private def run(process, args)
+      # When Ctrl+C is pressed, wait for the child process to handle the signal and finish -
+      # rather than us immediately exiting and leaving it to log "shutting down" messages from the background
+      Signal::INT.trap { }
+
       process.run command, args,
         output: STDOUT,
         error: STDERR,