Enhance sponsorship information in README

Updated sponsorship section to include project milestones.

Author: josevalim

README.md

@@ -36,7 +36,7 @@ editor to this binary.
 
 ## Sponsorship
 
-Thank you to our corporate sponsors! If you'd like to start sponsoring the project, please read more below.
+Thank you to our corporate sponsors! Expert is currently in alpha and [we have organized all future work, including the first release, as milestones](https://github.com/elixir-lang/expert/milestones). If you'd like to start sponsoring the project, please read more below.
 
 <div>
   <img height="100" src="./assets/sponsors/fly.png">