Write tests for DPUB-AAM role mapping

[cookiecrook]

We need DPUB computedrole tests for:
https://w3c.github.io/dpub-aam/#mapping_role_table

Possible Prerequisite: Does DPUB-AAM need a computedrole column added to the mapping table? I think the answer is likely "No" because in most cases, the computedrole will be the literal role name such as doc-chapter but I'd need to re-review the role mapping list.

Update: I do think we either need:

• a normative statement in DPUB-AAM that says ~"UAs MUST expose the literal role name as the computedrole", or
• a normative mapping column on the table... this second option would be easiest to update for example, if doc-chapter ever gets promoted to chapter in the core ARIA spec. Or if there are special cases, abstracts, and/or ignorables...

[cookiecrook]

Working on the prerequisite now:

• Define computedrole for doc-* roles w3c/dpub-aam#29

[cookiecrook]

Note: In w3c/dpub-aam#33 I added the column instead of the new RFC-2119 statement because this format can allow exceptions in the future... Quintessential example, if doc-chapter gets moved into Core-AAM, computedrole should return chapter not doc-chapter.

[cookiecrook]

Another example of when the column format would be more useful is if DPUB wants to expose any of the contextual role usage as generic, similar to how HTML-AAM and Core-AAM do in some places.