Add project status and roadmap to README

This commit adds a development status disclaimer and roadmap to the README file. The updated README file provides a clear timeline and stages of development for the project, which helps users understand the project's progress until its stable release. It also warns users not to use the current versions of the project in production until the stable release is out.

README.md

@@ -4,6 +4,19 @@ This is a Starter Kit for building SaaS applications using Supabase, Next.js, an
 
 This version uses Turborepo to manage multiple packages in a single repository.
 
+**This project is currently under development. Please wait for the stable release before using it in production.**
+
+### Roadmap
+
+The roadmap for the project is as follows:
+
+1. **March 31**: Alpha release - authentication, personal accounts, team accounts (memberships)
+2. **April 7**: Beta release - billing, Stripe, Lemon Squeezy, and more
+3. **April 14**: Release candidate - admin dashboard, translations, and more
+4. **April 21**: Final Release candidate - final features and improvements
+5. **April 28**: Stable release - final features and improvements
+6. **May 4**: Post-release - documentation, tutorials, and more
+
 ## Features
 
 - **Authentication**: Sign up, sign in, sign out, forgot password, update profile, and more.