Require C++17 to match ament_index_cpp 1.8.3+

Signed-off-by: Marco A. Gutierrez <marcogg@marcogg.com>

Author: marcoag

CMakeLists.txt

@@ -5,8 +5,8 @@ project(behaviortree_cpp_v3)
 set(CMAKE_CONFIG_PATH ${CMAKE_MODULE_PATH}  "${CMAKE_CURRENT_LIST_DIR}/cmake")
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CONFIG_PATH}")
 
-#---- Enable C++14 ----
-set(CMAKE_CXX_STANDARD 14)
+#---- Enable C++17 ----
+set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 if(MSVC)