add zksync example (#21)

* add zksync example

* lint fix

examples/zksync/.env-sample

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+# This is a sample .env file for use in local development.
+
+# Duplicate this file as .env here
+
+# Your Private key
+
+DEVNET_PRIVKEY="0x your key here"
+
+# Hosted Aggregator Node (JSON-RPC Endpoint). This is Arbitrum Sepolia Testnet, can use any Arbitrum chain
+
+L2RPC="https://sepolia.era.zksync.dev"
+
+# Ethereum RPC; i.e., for Sepolia https://sepolia.infura.io/v3/<your infura key>
+
+L1RPC=""
+
+# Arbitrum chain name
+ZKSYNC="ZKSYNCTEST"
+
+# Ethereum chain name
+ETHEREUM="SEPOLIA"

examples/zksync/.gitignore

@@ -0,0 +1 @@
+.env

examples/zksync/hardhat.config.js

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+require('@nomicfoundation/hardhat-toolbox');
+require('@matterlabs/hardhat-zksync-verify');
+require('./scripts/syncL2Requests');
+require('./scripts/syncBatchRoot');
+
+const BaseConfig = require('../../hardhat.base.config');
+
+module.exports = Object.assign({}, BaseConfig, {
+  paths: {
+    cache: '../../cache',
+    artifacts: '../../artifacts',
+  },
+});