Add the web interface

Plain HTML, CSS and JavaScript modules, with no build step. Hash routes
and relative URLs make it work under any path. The job list is polled:
every 2 seconds while a job runs, and less often otherwise.

tests/js/rule-fields.test.mjs

@@ -0,0 +1,11 @@
+import assert from 'node:assert/strict';
+import { readFileSync } from 'node:fs';
+import { test } from 'node:test';
+
+test('the monospace rule fields use the small text size, and stay as tall as the note field', () => {
+  const css = readFileSync(new URL('../../bindery/static/style.css', import.meta.url), 'utf8');
+  const rules = [...css.matchAll(/\.rule input:not\(\.rule-note\) \{([^}]*)\}/g)].map((m) => m[1]).join('');
+  for (const declaration of ['font-family: var(--mono)', 'font-size: var(--text-sm)', 'line-height: 1.5rem']) {
+    assert.ok(rules.includes(`${declaration};`), declaration);
+  }
+});