document propagation_styles.h

Author: dgoffredo

src/datadog/propagation_styles.h

@@ -1,5 +1,10 @@
 #pragma once
 
+// This component provides a `struct`, `PropagationStyles`, that specifies which
+// trace context extraction or injection formats are to be used. `TracerConfig`
+// has one `PropagationStyles` for extraction and another for injection. See
+// `tracer_config.h`.
+
 namespace datadog {
 namespace tracing {