README

Note: Much of this is yanked from https://github.com/aptos-labs/aptos-core/tree/main/crates/inspection-service. Unfortunately adding a dependency on that meant bringing in the whole Aptos codebase, including stuff that would require me to enable tokio unstable (not a huge deal, but just an indicator of how much extra code I'd be bringing in). So this is a stripped down, more tokio native version of the inspection service.