Move to Deno+Bunny.net, add a way to test webring locally.

test/webring_test.ts

@@ -0,0 +1,7 @@
+import { assertEquals } from '@std/assert';
+import { next } from '../src/webring.ts';
+
+Deno.test(function nextTest() {
+  const nextEntry = next('main');
+  assertEquals(nextEntry.id, 'dslog');
+});