feat: Implement EIP-155 (simple replay attack protection)

[rymnc]

EIP-155 requires the chainId to be set within the raw tx data, ref:

nim-web3/web3.nim

Lines 574 to 594 in 4c377e6

	proc send*(c: ContractCallBase,
	value = 0.u256,
	gas = 3000000'u64,
	gasPrice = 0): Future[TxHash] {.async.} =
	let
	web3 = c.web3
	gasPrice = if web3.privateKey.isSome() or gasPrice != 0: some(gasPrice)
	else: none(int)
	nonce = if web3.privateKey.isSome(): some(await web3.nextNonce())
	else: none(Nonce)
	cc = EthSend(
	data: "0x" & c.data,
	source: web3.defaultAccount,
	to: some(c.to),
	gas: some(Quantity(gas)),
	value: some(value),
	nonce: nonce,
	gasPrice: gasPrice)
	return await web3.send(cc)

This can be worked around by manually constructing the raw tx data, and including the chainId

[jangko]

fixed by #105, closing