Bind previous and next links to [ and ]

       document.documentElement.scrollTop -= 3 * em
     } else if (ev.key == 'l') {                      // l   go forward
       history.forward()
+    } else if (ev.key == '[') {                      // [   follow rel=prev
+      go(document.querySelector("a[rel=prev]").href)
+    } else if (ev.key == ']') {                      // ]   follow rel=next
+      go(document.querySelector("a[rel=next]").href)
     } else if (ev.key == 'w') {                      // w   TODO move up (in room)
     } else if (ev.key == 'a') {                      // a   TODO move left (in room)
     } else if (ev.key == 's') {                      // s   TODO move down (in room)