Add a table-of-content to device types page.

On the Device Types page, it wasn't really easy to get a clear overview of the device types that are described. You had to scroll through the whole page and hope you didn't miss any.

So I thought it would be more user-friendly to have a table-of-content at the top. This provides an easy overview of the device types on the page and allows you to quickly jump to the relevant section.

I kept the depth at 1 since it seemed too noisy to also include "Characteristics", "Optimal user experience" and "Example" for every device type. I also put the TOC after the introduction since that just seemed better than putting it all the way at the top.

I tested this locally and it just gives a bulleted list of links to the device types on the page. I did have to remove the backlinks from each section back to the TOC since that seemed to cause the styling on each section header to be removed. But it all looks good now.

Screenshot