parseInt from ENV var (#491)

contract-examples/hardhat.config.ts

@@ -4,7 +4,7 @@ import "./tasks.ts"
 // HardHat users must populate these environment variables in order to connect to their subnet-evm instance
 // Since the blockchainID is not known in advance, there's no good default to use and we use the C-Chain here.
 var local_rpc_uri = process.env.RPC_URI || "http://127.0.0.1:9650/ext/bc/C/rpc"
-var local_chain_id = process.env.CHAIN_ID || 99999
+var local_chain_id = parseInt(process.env.CHAIN_ID,10) || 99999
 
 export default {
   solidity: {