add `!.clear` command.

README.md

@@ -90,6 +90,7 @@ here are the commands that are specific to this REPL:
 
 - `!.exit` exits the REPL.
 - `!.env` prints out all the named functions.
+- `!.clear` clears the console.
 
 ## parentheses
 

src/repl.mjs

@@ -34,6 +34,8 @@ specials.set("!.env", _ => {
 	print(lines.join("\n"));
 });
 
+specials.set("!.clear", _ => console.clear());
+
 
 
 function run (line) {