[Docs] New page for generic accessibility classes and attributes

Created by: lonix1

Prerequisites

• I have searched for duplicate or closed feature requests
• I have read the contributing guidelines

Proposal

There are quite a number of pages in the docs which discuss accessibility.

It would be very helpful to have a new "accessibility" page which summarises all generic accessibility classes / aria attributes in one place. I'm not referring to accessibility specific to some component, but rather those bits that are generic.

For example, I always struggle to remember how to show visually and hide to screen readers, or vice versa (aria-hidden="true" and .visually-hidden). One of those has a dedicated page, and the other does not.

Motivation and context

I refer to the docs regularly. And I always find it difficult to find the bit that I'm looking for - I can't remember if it's under the "text", "reboot", "visibility", "visually hidden", etc., pages.