add image readme github code example

Example 1: add image to readme

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

Example 2: adding a preview image in readme.md

// method 1


// method 2
![Test Image 3](/3DTest.png)
![Test Image 4](https://github.com/tograh/testrepository/3DTest.png 112)

// last method

Example 3: github add image to readme

![GitHub Logo](/images/logo.png)
Format: ![Alt Text](url)

Example 4: how to add image in readme.md

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