add tracing adapter behind optional feature flag

[arferreira]

Description

• Implements tracing_subscriber::Layer via SheenLayer so sheen can capture events from the tracing ecosystem
• Any crate using tracing::info!(), tracing::warn!(), etc. gets routed through sheen's formatters
• Gated behind an optional tracing feature flag (sheen = {features = ["tracing"] })
• Updated README with tracing integration docs

Type of Change

• Bug fix
• New feature
• Documentation
• Refactor

Checklist

• cargo fmt ran
• cargo clippy passes
• cargo test passes
• Updated README if needed

Closes #3 (partial)

[MOZGIII]

Don't forget to disable default features if you don't use them

[MOZGIII]

Looks good at a glance, but see also my comment on the log adapter PR. Also appies here.

Keep in mind that tracing also has a log adapter - so you might to figure out how to deal with this situation where there are both tracing and log features active but there's also a tracing's log adapter enabled.

Also, don't forget to bench - your adapters might be mich quicker or much slower then the original crates themselves - and it'd be good to know.

[arferreira]

Looks good at a glance, but see also my comment on the log adapter PR. Also appies here.

Keep in mind that tracing also has a log adapter - so you might to figure out how to deal with this situation where there are both tracing and log features active but there's also a tracing's log adapter enabled.

Also, don't forget to bench - your adapters might be mich quicker or much slower then the original crates themselves - and it'd be good to know.

Yeahh, I'm aware about that! Good catches. I also fixed default-features on the tracing deps. I have two APIs for testing it and benchmarking will be on the radar for a follow-up as well.