Create README.md

This demo shows 
1.How to merge two video files into a single video file.
2.How to audio file to a video file.
3.Adding watermark(image & text) on video files.
4.Playing to video in parallel over another video file.

To use this demo, download file. There are simple four buttons & each of them has their body. You have to just replace your file name within code rest leave on us.