:page_facing_up: added code of conduct
:page_facing_up: added code of conduct

added Contributor Covenant Code of Conduct
nlohmann/json,kaidokert/json,hunter-packages/json,nlohmann/json,kaidokert/json,theodelrieu/json,theodelrieu/json,hunter-packages/json,hunter-packages/json,kaidokert/json,nlohmann/json