Add previous/next icons to header nav.

Author: BigBlueHat

index.js

@@ -15,7 +15,8 @@ const title = 'W3C API';
 const port = 8080;
 
 const app = new Application();
-app.use(browser({title}));
+app.use(browser({title, navigationLinks: {
+  previous: {priority: -1}, next: {priority: 1}}}));
 app.use(async ctx => {
   console.dir(ctx.request.requestTarget);
   if(ctx.request.requestTarget === '/') {