A brief description about what's in .env file
# Before deploying contract
API_URL = "https://eth-ropsten.alchemyapi.io/v2/<your-api-key>"
API_KEY = "<your-api-key>"
REACT_APP_ALCHEMY_KEY = "wss://eth-ropsten.ws.alchemyapi.io/v2/<your-api-key>"
PRIVATE_KEY = "<your-metamask-private-key>"
ETHERSCAN_API_KEY = "your-etherscan-key"
# After deploying contract
CONTRACT_ADDRESS = "0x<your contract address>"