feat: Do not send metrics if the client used DNT or GPC

cmd/rio/main.go

@@ -71,6 +71,8 @@ func handleSubdomain(ctx *context.GlobalContext, domain, cname, path string, req
 		Path:      path,
 		Referrer:  req.Header.Get("Referer"),
 		UserAgent: req.Header.Get("User-Agent"),
+		DNT:       req.Header.Get("DNT"),
+		GPC:       req.Header.Get("Sec-GPC"),
 		Writer:    w,
 		Global:    ctx,
 	}