Add `figcaption` styling to `twentysixteen` CSS.

themes/twentysixteen/css/style.css

@@ -2102,6 +2102,12 @@ body.search-no-results .page-header {
 	margin-bottom: 3.5em;
 }
 
+.entry-content figcaption,
+.entry-summary figcaption {
+    font-style: italic;
+    text-align: center;
+    padding-bottom: .5em;
+}
 
 /**
  * 11.3 - Post Formats