[çc] Add conformance-checker tests for <picture>
Remove .DS_Store
Test 1x and 1.0x
Add some srcset/sizes tests with empty value, single comma, multiple commas
Fix review comments
Add some tests for missing srcset on source
Fix review comments
Add a test with /**/ in srcset
Fix trailing css comment test
Fix aria region test name
Ban role=presentation
Merge pull request #1043 from zcorpan/cc-picture

[çc] Add conformance-checker tests for <picture>