Add haneul namespace and CAIP-2 spec

[GeunhwaJeong]

This PR adds documentation for the Haneul blockchain platform and a corresponding CAIP-2 specification which will unlock cross-chain integrations with Haneul.

[GeunhwaJeong]

Testnet RPC Endpoint

URL: http://51.75.242.118:9000

1. Chain Identifier Verification (CAIP-2)

curl -s -X POST http://51.75.242.118:9000 \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"haneul_getChainIdentifier","params":[]}'

Expected response:

{"jsonrpc":"2.0","id":1,"result":"afd5afb7"}

2. Network Activity Verification

curl -s -X POST http://51.75.242.118:9000 \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"haneul_getLatestCheckpointSequenceNumber","params":[]}'

Expected response (checkpoint number will increase over time):

{"jsonrpc":"2.0","id":1,"result":"2603412"}