fix: shimmer has the potential to cover images (#1100)

Resolves #1100

_sass/addon/commons.scss

@@ -91,6 +91,7 @@ img {
       &.lazyloaded {
         -webkit-animation: fade-in 0.35s ease-in;
         animation: fade-in 0.35s ease-in;
+        z-index: 0;
       }
     }