add flex: auto to article so it expands to available width

src/css/doc.css

@@ -10,6 +10,7 @@
 
 @media screen and (min-width: 1024px) {
   .doc {
+    flex: auto;
     font-size: var(--doc-font-size--desktop);
     margin: var(--doc-margin--desktop);
     max-width: var(--doc-max-width--desktop);