Allow addition of one or more WCAG level AAA criteria, without adding all of AAA

[mitchellevan]

It would be useful to generate a report with all of WCAG Level A and AA criteria, plus a single level AAA criterion. (Or potentially more than one.)

See issue #345 for a nice formatting option.

Israel Standard (IS) 5568 (PDF, Hebrew) is based on WCAG 2.0 Level A and AA, with the addition of 2.4.10 Section Headings (Level AAA). As far as I know, Israel's is the only national regulation that adds any portion of level AAA.

A few companies and organizations choose to include a subset of AAA criteria in testing, but so far I haven't seen any formal conformance reports based on that.