[www] ArticleCard style impoved: use % width

src/style/components/ArticleCard.scss

@@ -2,9 +2,12 @@
   display: flex;
   flex-direction: column;
 
-  margin: .25em;
+  margin: var(--single-margin) var(--half-margin);
+
+  width: 30%;
+  min-width: 15em;
   max-width: 30em;
-  
+
   border: 1px solid #ccc;
   border-radius: 3px;
 }