This video will help you to enable the CORS (CrossOrigin Resource Sharing ) in Geoserver and Tomcat.

text file having content to paste in tomcat web.xml file:
https://drive.google.com/file/d/10Y6H...

Timeline of the Video:
00:00 Introduction
03:00 Enable CORS using web.xml file of Tomcat(if geoserver war file deployed in Tomcat)
07:00 Enable CORS using web.xml file of Geoserver deployed inside Tomcat (if geoserver war file deployed in Tomcat)
10:40 Enable CORS using web.xml file of Geoserver (if geoserver is installed directly using platorm independent binary)