fix: fix side-effect of jQuery .filter() in Abide.addA11yAttributes
fix: fix side-effect of jQuery .filter() in Abide.addA11yAttributes

Prevent jQuery `.filter()` to mutate the context object.

zurb/foundation-sites,atmmarketing/foundation-sites,zurb/foundation,DaSchTour/foundation-sites,atmmarketing/foundation-sites,denisahac/foundation-sites,DaSchTour/foundation-sites,zurb/foundation-sites,zurb/foundation-sites,dragthor/foundation-sites,abdullahsalem/foundation-sites,abdullahsalem/foundation-sites,denisahac/foundation-sites,dragthor/foundation-sites,abdullahsalem/foundation-sites,colin-marshall/foundation-sites,colin-marshall/foundation-sites,zurb/foundation,dragthor/foundation-sites,denisahac/foundation-sites,zurb/foundation,colin-marshall/foundation-sites,atmmarketing/foundation-sites