Add cache-control header to nginx for html files (#1374)

Signed-off-by: Jamon Camisso <[email protected]>

nginx.conf

@@ -99,6 +99,10 @@ http {
             rewrite ^ /vulnerabilities/index.html break;
         }
 
+        location ~* /(\index.html)?$ {
+            add_header Cache-Control "public, max-age=300, stale-while-revalidate=300";
+        }
+
 	# use hugo's built in 404 page for now
 	error_page 404 /404.html;