how to add image in readme.md file code example

Example 1: add image to readme

![alt text](http://url/to/img.png)

Example 2: add image to readme

![alt text](https://github.com/[username]/[reponame]/blob/[branch]/image.jpg?raw=true)

Example 3: github adding images to readme

![alt text](http://url/to/img.png)