[FIX] website: responsive images in table for Firefox only

It looks there is a bug in Firefox concerning responsive images in table. See bugzilla https://bugzilla.mozilla.org/show_bug.cgi?id=975632
Bootstrap advises to use width: 100% for .img-responsive as workaround were needed.
The @moz-document is to apply this for Mozilla only.

opw-617582
opw-618659

addons/website/static/src/css/website.css

@@ -194,6 +194,11 @@ footer {
   width: 100%;
 }
 
+@-moz-document url-prefix() {
+  .table .img-responsive {
+    width: 100%;
+  }
+}
 /* ---- HACK FOR COVERING UP CK EDITOR BOGUS P INSERTION --- */
 .oe_structure.oe_editable.oe_empty:empty, .oe_editable[data-oe-type=html]:empty, .oe_structure.oe_editable.oe_empty > .oe_drop_zone.oe_insert:only-child, [data-oe-type=html] > .oe_drop_zone.oe_insert:only-child {
   background-image: url("/website/static/src/img/drag_here.png") !important;

addons/website/static/src/css/website.sass

@@ -147,6 +147,10 @@ footer
     float: left
     width: 100%
 
+@-moz-document url-prefix()
+    .table .img-responsive
+        width: 100%
+
 /* ---- HACK FOR COVERING UP CK EDITOR BOGUS P INSERTION --- */
 
 .oe_structure.oe_editable.oe_empty:empty, .oe_editable[data-oe-type=html]:empty, .oe_structure.oe_editable.oe_empty > .oe_drop_zone.oe_insert:only-child, [data-oe-type=html] > .oe_drop_zone.oe_insert:only-child