feat(client): define constants and validation for DSCP and server fill

crates/irtt-client/src/lib.rs

@@ -11,7 +11,10 @@ mod socket;
 mod timing;
 
 pub use client::Client;
-pub use config::{ClientConfig, NegotiationPolicy, RecvBudget, RunMode, SocketConfig};
+pub use config::{
+    ClientConfig, NegotiationPolicy, RecvBudget, RunMode, SocketConfig, MAX_DSCP_CODEPOINT,
+    MAX_SERVER_FILL_BYTES,
+};
 pub use error::{ClientError, EventSubscriptionError};
 pub use event::{
     ClientEvent, OneWayDelaySample, OpenOutcome, PacketMeta, ReceivedStatsSample, RttSample,