Added 'backlight' property to LCD options for 'johnny-five'.

johnny-five/johnny-five.d.ts

@@ -251,10 +251,12 @@ declare module "johnny-five" {
 
     export interface LCDI2COption extends LCDGeneralOption{
         controller: string;
+        backlight?: number;
     }
 
     export interface LCDParallelOption extends LCDGeneralOption{
         pins: Array<any>;
+        backlight?: number;
     }
 
     export class LCD{