providers: Fix viem non-public clients, wrap autoload ENS error

[shazow]

• Reformatted some tests, ignore whitespace plz
• Added explicit viem example to the README, so it's more clear that whatsabi is not ethers-only (fixes #106)
• Added AutoloadError wrapper for when provider does not support ENS with instructions to specify addressResolver
• Added test for passing in a fake provider without ENS support
• Refactored the provider abstraction to be a bit more EIP-1193-centric.
• Default viem test suite now runs with a createWalletClient instead of a createPublicClient
• Fixes #105 ?

Obsoletes #104