Add log compatibility

See https://docs.rs/tracing/latest/tracing/#emitting-log-records. Would be helpful for use in python extension crates that want to use pyo3-log

Thank you for the PR!

Shouldn't this be a feature flag in https://github.com/64bit/async-openai/blob/main/async-openai/Cargo.toml#L15-L24 to opt in explicitly? May be tracing-log = [ "tracing/log" ]

Since the library is not using the feature flag directly, it doesn't need to be enabled by default. Open to hear why you'd like to enable it by default?

Oh, that sounds reasonable actually. Although in that case maybe tracing itself should also be enabled by a feature? I tried looking for examples in libraries I expected to have something like this, but apparently they don't have a way to enable tracing-log either. I wonder if I'm missing something.

Anyway it's your decision of course