add NAKB example

src/viewer/index.html

@@ -621,6 +621,15 @@
                             kind: 'density'
                         }
                     }
+                },
+                {
+                    id: '5MRX',
+                    info: 'RNA sarcin-ricin loop',
+                    config: {
+                        props: {
+                            kind: 'nakb'
+                        }
+                    }
                 }
             ];