closes #375

The purpose of this proposal is both to resolve the issue that "scoped" was an undefined term that was used to indicate when certain elements would expose particular ARIA roles or not.  However, in the year of noodling on this, other activities to revise what "owned" means in ARIA, the idea of a minimum role, as well as the fact there were other elements in HTML that have "scoped" or "contextual roles" that are based on heuristics, rather than defined standards, became relevant.

A change to hopefully help simplify the implementations of contextual roles is that this proposal is aiming to tie the role of an element based on its a11y tree ancestry, rather than based on specific HTML elements in the DOM.

This PR represents the initial draft of the proposal.  Other work to explicitly call out the elements that have contextual roles, what roles they need to adjust to, and other wording revisions to replace "scoped" with the new term would still need to be made.

still working on the exact wording.  also changing some placeholder short code so as to hopefully not get more build errors for presently undefined terms

Co-authored-by: James Craig <cookiecrook@users.noreply.github.com>

Co-authored-by: James Craig <cookiecrook@users.noreply.github.com>

use computed role in both sentences, rather than switching between terms

Co-authored-by: James Craig <cookiecrook@users.noreply.github.com>