docs: include React 19 blog post in sidebarBlog.json (#7331)

Author: slorber

src/sidebarBlog.json

@@ -11,6 +11,13 @@
       "path": "/blog",
       "skipBreadcrumb": true,
       "routes": [
+        {
+          "title": "React 19",
+          "titleForHomepage": "React 19",
+          "icon": "blog",
+          "date": "December 05, 2024",
+          "path": "/blog/2024/12/05/react-19"
+        },
         {
           "title": "React Compiler Beta Release and Roadmap",
           "titleForHomepage": "React Compiler Beta Release and Roadmap",