Bug 1509867 - add moz.yaml to libpng, r=aosmond

Differential Revision: https://phabricator.services.mozilla.com/D12901

--HG--
extra : moz-landing-system : lando

media/libpng/MOZCHANGES

@@ -1,5 +1,6 @@
 
 Changes made to pristine libpng source by mozilla.org developers.
+Update the 'release' field in moz.yaml when you update this file.
 
 2018/09/14  -- Synced with libpng-1.6.35 (bug #1491467).
 

media/libpng/moz.yaml

@@ -0,0 +1,14 @@
+schema: 1
+
+bugzilla:
+  product: "Core"
+  component: "ImageLib"
+
+origin:
+  name: "libpng"
+  description: "PNG reference library"
+
+  url: "http://www.libpng.org/pub/png/libpng.html"
+  license: "libpng"
+
+  release: "1.6.35"