Add support contact note for higher CPU/RAM limits

Users can now see they should contact support@e2b.dev if they need
higher CPU or RAM limits than the defaults.

Author: beran-t

docs/billing.mdx

@@ -64,6 +64,10 @@ Template.build(
 
 See [template quickstart](/docs/template/quickstart) for more details on building custom templates.
 
+<Note>
+Need higher CPU or RAM limits? Contact [support@e2b.dev](mailto:support@e2b.dev) for more information.
+</Note>
+
 ---
 
 ## Monitoring usage