feat: add support for L2 contracts

[tmigone]

Motivation

This PR adds support for the soon to come L2 contracts.

Changes

• The connectContracts function now returns the contracts for either L1 or L2 depending on the chainId used.
• Added GraphChain utilities with some generic L1/L2 related methods.

Examples

import { connectContracts, GraphChain } from '@graphprotocol/common-ts'

// Get mainnet contracts
const l1Contracts  = await connectContracts(provider, 1)

// Get Arbitrum One contracts
const l2Contracts  = await connectContracts(provider, 42161)

// Chain utilities - see source code for more
const chainId = 1
console.log(GraphChain.l1Chains())
console.log(`Chain Id ${chainId} is L${GraphChain.isL1(chainId) ? '1' : '2'}`)
console.log(`Counterpart chain Id for chain ${chainId} is ${GraphChain.counterpart(chainId)}`)

Signed-off-by: Tomás Migone tomas@edgeandnode.com

[pcarranzav]

LGTM 🤖