Fix prelude/url (#7855)

test/prelude/url.ts

@@ -0,0 +1,13 @@
+import * as assert from 'assert';
+import { query } from '../../src/prelude/url';
+
+describe('url', () => {
+	it('query', () => {
+		const s = query({
+			foo: 'ふぅ',
+			bar: 'b a r',
+			baz: undefined
+		});
+		assert.deepStrictEqual(s, 'foo=%E3%81%B5%E3%81%85&bar=b%20a%20r');
+	});
+});