chore: improve readme with badges and project status

README.md

@@ -1,7 +1,16 @@
 # 🍲 Mabo
 
+[![GitHub License](https://img.shields.io/github/license/dnaka91/mabo?style=for-the-badge)](LICENSE.md)
+[![GitHub commit activity](https://img.shields.io/github/commit-activity/m/dnaka91/mabo?style=for-the-badge&logo=git)](https://github.com/dnaka91/mabo/commits/main/)
+[![Discord](https://img.shields.io/discord/789699970138767360?style=for-the-badge&logo=discord)](https://discord.gg/phxGsW8dWd)
+[![GitHub Sponsors](https://img.shields.io/github/sponsors/dnaka91?style=for-the-badge&logo=githubsponsors)](https://github.com/sponsors/dnaka91)
+
 Data format and schema, with a type system as strong as Rust's.
 
+This project is currently still in a _pre-alpha_ stage and undergoing many changes until the first alpha release. Nonetheless, it should already be usable from the Rust side but expect breaking changes often.
+
+For further details about how to get started, the schema language or anything else, please consult the official [project website](https://dnaka91.github.io/mabo/).
+
 ## License
 
 This project is licensed under [MIT License](LICENSE.md) (or <http://opensource.org/licenses/MIT>).