Update README.md

Author: damianmalczewski

README.md

@@ -43,6 +43,17 @@ Instead of releasing version `2.0`, library was split into two modules, because
 - ✅ Pluggable via Jackson's `Module` system or predefined `MixIn` interface.
 - ✅ Lightweight, with no external dependencies beyond Jackson and `problem4j-core`.
 - ✅ Support for both Jackson2 (`com.fasterxml.jackson`) and Jackson3 (`tools.jackson`).
+- ✅ Integrated with JSpecify annotations for nullability and Kotlin interop (since `v1.4.0`).
+- ✅ Supports **Java Platform Module System** (since `v1.4.0`). Artifact for `problem4j-jackson2` uses multi-release JAR
+  to support Java 8 and Java 9+ module system, while artifact for `problem4j-jackson3` is compiled with Java 17 and
+  supports module system out of the box.
+  ```java
+  module org.exmple.project {
+    // pick the one for your project
+    requires io.github.problem4j.jackson2;
+    requires io.github.problem4j.jackson3;
+  }
+  ```
 
 ## Example