Promote Visually Hidden Class

[isosphere]

Bootstrap supports a visually hidden class that is intended to be used to add context and information to screen readers that would otherwise only be conveyed visually, i.e.: with colours or symbols.

I'd like us to incorporate this somehow in a way that is very easy to use, to promote the creation of accessible web interfaces.

I think I'd like this to happen via separate components rather than boolean switches applied to existing components, even though the latter is more efficient and logical strictly from a software design perspective. I'd like us to wear our user experience caps here and have this jump out at people as a set of tools to use to communicate to folks using screen readers.

I don't think we can just subclass things in Rust, so that's going to be a bit messy - but we don't need to support any visual features with these components.