update core media type requirements for picture and img#1247

Merged

dauwhe merged 2 commits intomasterfrom fix/issue-1237/revised-cmt

Mar 21, 2019

+17-9

Commits on Mar 14, 2019

update core media type requirements for img/source/src/srcset as described in issue #1237
mattgarrish
committed
updates to wording as requested by rdeltour
mattgarrish
committed