Added class diagram test case with C++20 module partitions

tests/t00072/src/lib2.cppm

@@ -0,0 +1,13 @@
+export module t00072.app:lib2;
+
+export namespace clanguml::t00072 {
+class C { };
+
+template <typename T> class CC {
+    T t;
+};
+
+namespace detail {
+enum class CCC { ccc1, ccc2 };
+}
+}