Enhance introduction of CoreCast documentation

Added a header to the introduction section and clarified the description of Smart gRPC Streams.

Author: divyasshree-BQ

docs/grpc/solana/introduction.md

@@ -3,6 +3,8 @@ title: CoreCast - Smart Solana gRPC Streams
 description: Low-latency, context-aware, topic-wise streaming from Bitquery for onchain data over gRPC.
 ---
 
+# CoreCast - Smart Solana gRPC Streams
+
 ### What are Smart gRPC Streams?
 
 Bitquery Smart gRPC Streams provide low-latency, context-aware, topic-wise event delivery from the Solana blockchain. Unlike raw gRPC streams, Smart Streams enrich and filter events so your application receives only the data it needs (trades,balances, token context, program metadata). The data is sent in the **protobuf format**, the schema is publicly available as packages for easy parsing.