Added documentation on how TCK test cases can be packaged in DMN files

utils/dmn-tck-packager/README.md

@@ -2,6 +2,21 @@
 
 This utility can package/extract DMN TCK Test Cases file in DMN XML file extended attributes.
 
+The TCK test cases are packaged in the DMN model `definitions` level as an `extensionElements`.
+
+```
+<semantic:definitions xmlns:semantic="https://www.omg.org/spec/DMN/20211108/MODEL/" xmlns:tc="http://www.omg.org/spec/DMN/20160719/testcase">
+    <semantic:extensionElements>
+        <tc:testCases>
+            <tc:testCase id="tc-1" name="Test Case 1">
+				...
+			</tc:testCase>
+            <tc:testCase id="tc-2" name="Test Case 2">
+				...
+			</tc:testCase>
+		</tc:testCases>
+</semantic>
+```
 
 
 ## Building the Packager