repl: clear screen and help menu

compiler/repl.v

@@ -5,6 +5,7 @@
 module main
 
 import os
+import term
 
 struct Repl {
 mut:
@@ -49,6 +50,15 @@ fn (r mut Repl) function_call(line string) bool {
 	return false
 }
 
+fn repl_help() {
+println('
+V $Version
+  help                   Displays this information.
+  Ctrl-C, Ctrl-D, exit   Exits the REPL.
+  clear                  Clears the screen.
+')
+}
+
 fn run_repl() []string {
 	println('V $Version')
 	println('Use Ctrl-C or `exit` to exit')
@@ -80,6 +90,14 @@ fn run_repl() []string {
 		if line == '\n' {
 			continue
 		}
+		if line == 'clear' {
+			term.erase_display('2')
+			continue
+		}
+		if line == 'help' {
+			repl_help()
+			continue
+		}
 		if line.starts_with('fn') {
 			r.in_func = true
 			r.functions_name << line.all_after('fn').all_before('(').trim_space()