user types CHANGE a new installed user type example

It does only validation, so user can work with
all the values just like before.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 82c10cd..b96f56b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -269,6 +269,9 @@
 # YANG extensions plugins
 add_subdirectory(src/extensions)
 
+# YANG user types plugins
+add_subdirectory(src/user_types)
+
 # yanglint
 add_executable(yanglint ${lintsrc})
 target_link_libraries(yanglint yang)