Add npm badge

[seveibar]

[AdarshNiket]

Hi Severin,

Below is the code to add npm badge in your Readme file. I hope I am not interrupting you by doing this. If I am kindly let me know, else I will go ahead and create a PR for this if that's fine by you. Thank you in advance.

![npm ](https://img.shields.io/npm/v/npm)