Integrate Keystatic to edit twenty.com content (#10709)

This PR introduces Keystatic to let us edit twenty.com's content with a
CMS. For now, we'll focus on creating release notes through Keystatic as
it uses quite simple Markdown. Other types of content will need some
refactoring to work with Keystatic.


https://github.com/user-attachments/assets/e9f85bbf-daff-4b41-bc97-d1baf63758b2

---------

Co-authored-by: Félix Malfait <felix@twenty.com>

packages/twenty-website/package.json

@@ -15,6 +15,9 @@
   },
   "dependencies": {
     "@docsearch/react": "^3.6.2",
+    "@keystatic/core": "^0.5.45",
+    "@keystatic/next": "^5.0.3",
+    "@markdoc/markdoc": "^0.5.1",
     "@nivo/calendar": "^0.87.0",
     "gray-matter": "^4.0.3",
     "next-runtime-env": "^3.2.2",