Responsive jupyterbook images

Currently we are using the following format to include figures in the posts.

```

>    ```{figure} ../figures/png/vdi_8.png
>    ---
>    width: 480px
>    name: vdi_8
>    ``` 

```

There is a `scale` option, however, it refers to the original image size not the text size. It would be good to make the scaling responsive.  