feat(network): implement GetChainBlockNo local state query (#441)

pallas-network/src/miniprotocols/localstate/queries_v16/mod.rs

@@ -91,6 +91,15 @@ pub struct SystemStart {
     pub picoseconds_of_day: u64,
 }
 
+#[derive(Debug, Encode, Decode, PartialEq)]
+pub struct ChainBlockNumber {
+    #[n(0)]
+    pub slot_timeline: u32,
+
+    #[n(1)]
+    pub block_number: u32,
+}
+
 #[derive(Debug, PartialEq, Eq, Clone)]
 pub struct RationalNumber {
     pub numerator: u64,
@@ -368,6 +377,14 @@ pub async fn get_system_start(client: &mut Client) -> Result<SystemStart, Client
     Ok(result)
 }
 
+/// Get the block number for the current tip.
+pub async fn get_chain_block_no(client: &mut Client) -> Result<ChainBlockNumber, ClientError> {
+    let query = Request::GetChainBlockNo;
+    let result = client.query(query).await?;
+
+    Ok(result)
+}
+
 /// Get the current protocol parameters.
 pub async fn get_current_pparams(
     client: &mut Client,