[user_events] Add dependence to eventheader-headers which provides header files for include#554

ThomsonTan merged 1 commit intoopen-telemetry:mainopen-telemetry/opentelemetry-cpp-contrib:mainfrom

ThomsonTan:add_event_headerThomsonTan/opentelemetry-cpp-contrib:add_event_headerCopy head branch name to clipboard