Check accessibility of toolkit

Check e.g. alt text for images, contrast etc.

See for example [this page](https://cfpb.github.io/design-manual/data-visualization/accessibility.html#alt-tags) and [these posters](https://github.com/UKHomeOffice/posters/blob/master/accessibility/dos-donts/posters_en-UK/accessibility-posters-set.pdf).