Move `.env` to `.env.example` #1745

Job	Run time
solidity-slither	1m 6s
solidity-build / build-solidity	47s
solidity-format	49s
solidity-test	34s
solidity-integration-test	56s
solidity-deploy-dry-run	30s
solidity-deploy-testnet	0s
	4m 42s

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