Added initial support for include graph diagrams

tests/t40001/include/t40001_include1.h

@@ -0,0 +1,9 @@
+#pragma once
+
+#include "lib1/lib1.h"
+
+namespace clanguml::t40001 {
+
+int foo() { return lib1::foo2(); }
+
+}

tests/t40001/src/t40001.cc

@@ -1,7 +1,7 @@
 #include <string>
 #include <vector>
 
-#include "t40001_include1.h"
+#include "include/t40001_include1.h"
 
 namespace clanguml {
 namespace t40001 {

tests/t40001/t40001_include1.h

@@ -1,7 +0,0 @@
-#pragma once
-
-namespace clanguml::t40001 {
-
-int foo() { return 0; }
-
-}