Add re-watch banner for React Conf Keynote 2024 (facebook#4199)

Author: cortinico

website/docusaurus.config.js

@@ -213,9 +213,9 @@ module.exports = {
     /** @type {import('@docusaurus/preset-classic').ThemeConfig} */
     ({
       announcementBar: {
-        id: 'support_ukraine',
+        id: 'reactconf2024-keynote',
         content:
-          'Support Ukraine 🇺🇦 <a target="_blank" rel="noopener noreferrer" href="https://opensource.facebook.com/support-ukraine"> Help Provide Humanitarian Aid to Ukraine</a>.',
+          'Re-watch the <a target="_blank" rel="noopener noreferrer" href="https://youtu.be/Q5SMmKb7qVI?si=c-6kFImfKFHdw2lc">React Native Keynote</a> @ React Conf 2024.',
         backgroundColor: '#20232a',
         textColor: '#fff',
         isCloseable: false,