Add comment, test to unescapeHTML (#7949)

app/javascript/mastodon/utils/__tests__/html-test.js

@@ -0,0 +1,10 @@
+import * as html from '../html';
+
+describe('html', () => {
+  describe('unsecapeHTML', () => {
+    it('returns unescaped HTML', () => {
+      const output = html.unescapeHTML('<p>lorem</p><p>ipsum</p><br>&lt;br&gt;');
+      expect(output).toEqual('lorem\n\nipsum\n<br>');
+    });
+  });
+});