Add rate limiting options for @wagmi/cli block explorer plugins

[tyko0x]

Block explorers like etherscan often have strict rate limiting: https://etherscan.io/apis. For example, under the free etherscan plan, if you are fetching more than 5 ABIs, then the plugins errors out since the rate limit is 5 calls per second.

I suggest adding some rate limiting options - such as limit and interval options.