feat: Update example RPCs (#22)

.env.example

@@ -6,17 +6,17 @@ LEDGER_SENDER=
 PRIVATE_KEY=
 
 # Test rpc_endpoints
-RPC_MAINNET=https://rpc.flashbots.net
+RPC_MAINNET=https://eth.llamarpc.com
 RPC_AVALANCHE=https://api.avax.network/ext/bc/C/rpc
-RPC_OPTIMISM=https://mainnet.optimism.io
-RPC_POLYGON=https://polygon-rpc.com
-RPC_ARBITRUM=https://arb1.arbitrum.io/rpc
+RPC_OPTIMISM=https://optimism.llamarpc.com
+RPC_POLYGON=https://polygon.llamarpc.com
+RPC_ARBITRUM=https://arbitrum.llamarpc.com
 RPC_FANTOM=https://rpc.ftm.tools
 RPC_HARMONY=https://api.harmony.one
 RPC_METIS=https://andromeda.metis.io/?owner=1088
-RPC_BASE=https://mainnet.base.org
+RPC_BASE=https://base.llamarpc.com
 RPC_ZKEVM=https://zkevm-rpc.com
-RPC_GNOSIS=https://rpc.gnosischain.com
+RPC_GNOSIS=https://rpc.ankr.com/gnosis
 RPC_BNB=https://binance.llamarpc.com
 
 # Etherscan api keys for verification & download utils