doc(uml): add class diagram

doc/uml/class-diagram.md

@@ -0,0 +1,26 @@
+Julienne Unit Testing Classes
+-----------------------------
+```mermaid
+classDiagram
+
+class string_t
+class test_t
+class test_result_t
+class test_description_t
+class test_diagnosis_t
+class vector_test_description_t
+
+class test_t{
+  <<abstract>>
+    + subject() character
+    + results() test_result_t
+    + report()
+}
+class vector_test_description_t{
+  <<abstract>>
+    - description_vector_ : string_t
+    - vector_function_strategy_ : vector_function_strategy_t
+    + vector_function() string_t
+}
+
+vector_test_description_t o-- string_t