cli: add 'q' as an alias for 'quit' (#525)

Fixes #524

Co-authored-by: Alexey Alexandrov <aalexand@users.noreply.github.com>

internal/driver/commands.go

 	} else {
 		help = "  Commands:\n"
 		commands = append(commands, fmtHelp("o/options", "List options and their current values"))
-		commands = append(commands, fmtHelp("quit/exit/^D", "Exit pprof"))
+		commands = append(commands, fmtHelp("q/quit/exit/^D", "Exit pprof"))
 	}
 
 	help = help + strings.Join(commands, "\n") + "\n\n" +

internal/driver/interactive.go

 			case "o", "options":
 				printCurrentOptions(p, o.UI)
 				continue
-			case "exit", "quit":
+			case "exit", "quit", "q":
 				return nil
 			case "help":
 				commandHelp(strings.Join(tokens[1:], " "), o.UI)