Present the widgets from the readme

[vinyll]

This reposity seems to be a great resource for Grist!

However it's not so obvious to be aware of all the work done here and which component does what.

Some proposals could be either:

• having a list of the widgets with a tiny description
• present a screenshot of the widget within a context
• …

[paulfitz]

Yes!! This would be great. I think it would be quite practical in fact to present not just screenshots but live examples, now that grist-static exists.