Add note to readme

README.md

@@ -15,8 +15,14 @@ An experimental Java library for embedding a Lua VM.
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+This project allows executing Lua scripts from a Java application. It uses [Foreign Function & Memory API (JEP 454)](https://openjdk.org/jeps/454) for accessing the Lua C API.
+
 ## Development
 
+### Native Interface
+
+Build scripts generate native interface classes in `build/generated/sources/jextract` using [Jextract](https://github.com/openjdk/jextract). Scripts download and cache Jextract automatically during the build.
+
 ### Check for Dependency Updates
 
 ```sh