Widget overview in documentation not clear and incomplete

Hi guys,

The [widget overview](https://dashboard.flowfuse.com/nodes/widgets.html) in the documentation is a really great place to get started. I really like it.

But it might need some improvements:

1. Some widgets (e.g. button group) are missing in this overview.

2. The images are not very clear. For example this is what I see on my Windows portable:


While the widgets themselves look very nice, you don't see them that way in these pictures. Not sure how that can be solved, but this way I don't think we will attract much new users searching for an attractive dashboard to be honest.