feat: add hook data support

src/main/java/dev/openfeature/sdk/DefaultHookData.java

@@ -0,0 +1,39 @@
+package dev.openfeature.sdk;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Default implementation of HookData.
+ */
+public class DefaultHookData implements HookData {
+    private Map<String, Object> data;
+
+    @Override
+    public void set(String key, Object value) {
+        if (data == null) {
+            data = new HashMap<>();
+        }
+        data.put(key, value);
+    }
+
+    @Override
+    public Object get(String key) {
+        if (data == null) {
+            return null;
+        }
+        return data.get(key);
+    }
+
+    @Override
+    public <T> T get(String key, Class<T> type) {
+        Object value = get(key);
+        if (value == null) {
+            return null;
+        }
+        if (!type.isInstance(value)) {
+            throw new ClassCastException("Value for key '" + key + "' is not of type " + type.getName());
+        }
+        return type.cast(value);
+    }
+}