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

tests/t00072/src/t00072_mod.cppm

@@ -0,0 +1,13 @@
+export module t00072.app;
+export import :lib1;
+export import :lib1.mod1;
+export import :lib1.mod2;
+export import :lib2;
+
+export namespace clanguml::t00072 {
+class A {
+    int get() { return a; }
+
+    int a;
+};
+}