docs: add Deploy demo app page (partial), change prism theme to palenight

docs/docusaurus.config.js

@@ -144,8 +144,8 @@ const config = {
         ]
       },
       prism: {
-        theme: prismThemes.github,
-        darkTheme: prismThemes.dracula,
+        theme: prismThemes.palenight,
+        //darkTheme: prismThemes.dracula,
       },
     }),
 };