[dev] gantt instance is now passed to custom form

Author: AlexKlimenkov

docs/integrations/react/overview.md

@@ -348,13 +348,15 @@ import React, { useState } from 'react';
 
 export interface CustomLightboxProps {
   data: any;
+  gantt: any;
   onSave: (task: any) => void;
   onCancel: () => void;
   onDelete: () => void;
 }
 
 const CustomLightbox: React.FC<CustomLightboxProps> = ({
   data,
+  gantt,
   onSave,
   onCancel,
   onDelete