added vim modeline to sources

cli.rkt

@@ -1,5 +1,6 @@
 #! /usr/bin/env racket
 #lang racket
+; vim: set tw=80 :
 
 (require "interpreter.rkt"
          racket/block)

gui.rkt

@@ -1,4 +1,5 @@
 #lang racket/gui
+; vim: set tw=80 :
 
 (require "interpreter.rkt"
          framework
@@ -250,4 +251,4 @@
 (append-editor-operation-menu-items m-edit #f)
 (send EDITOR set-max-undo-history 100)
 (send C set-editor EDITOR)
-(send F show #t)
+(send F show #t)

interpreter.rkt

@@ -1,4 +1,5 @@
 #lang racket
+; vim: set tw=80 :
 
 ; 2018-11-21 - Made by Claudio Maggioni - Tommaso Rodolfo Masera
 ; easybf