Added a duck image

[Kapil564]

Description

Here my contribution to "The Duck Gallery".

You must respect the following conditions

1. Your contribution must respect the code of conduct
2. It's your first PR to this repository
3. You have added your image of the duck downloaded from https://pimpmyduck.zenika.com
4. You have not changed the image of the duck
5. The image filename must be your GitHub username (ex: your-username.png)
6. You are using your own GitHub user and it's the same as the PR author
7. Into the contributors.js file, the message must be short and respect the code of conduct

If the PR doesn't respect those conditions, it will be closed

[jeanphi-baconnais]

Thanks for this contribution