Prepare tracing-appender for release

[thekeys93]

Following the release process for https://github.com/tokio-rs/tracing/blob/master/CONTRIBUTING.md and these changes are the only things left to commit before release.

I'd like to hopefully get this released today so we can start using this crate internally.

Note:
I need to get PR #703 and PR #678 merged before release.

[hawkw]

I think there is a little more to do to get this ready to release. Let's also update the Cargo.toml to contain the standard set of metadata that other crates in the project have:

tracing/tracing/Cargo.toml

Lines 13 to 27 in 5a971be

	license = "MIT"
	readme = "README.md"
	repository = "https://github.com/tokio-rs/tracing"
	homepage = "https://tokio.rs"
	description = """
	Application-level tracing for Rust.
	"""
	categories = [
	"development-tools::debugging",
	"development-tools::profiling",
	"asynchronous",
	"no-std",
	]
	keywords = ["logging", "tracing", "metrics", "async"]
	edition = "2018"

(but don't add the no-std category because this crate does require the standard library)

Also, I'd like to give this crate a quick final API pass before publishing in case we need to change anything up.

I'd like to hopefully get this released today so we can start using this crate internally.

If you want to use the crate before it's ready to release, are you able to take a git dependency temporarily?

[hawkw]

Note:
I need to get PR #703 and PR #678 merged before release.

I don't think it's necessary to block a crates.io release on the benchmarks. They aren't part of the crate's API and will primarily be useful internally for development purposes. I would like to merge the tests first, though.

[thekeys93]

I'd like to hopefully get this released today so we can start using this crate internally.

If you want to use the crate before it's ready to release, are you able to take a git dependency temporarily?

Unfortunantely we aren't able to take a git dependency. The only way for us to use this is if there is a crate available for us.

[hawkw]

Okay, this looks great! I'll get a release out soon.

Thanks again for all your hard work on this, @zekisherif!

If you have the chance, it would also be nice to have a follow-up PR adding this crate to the list of crates in the project here.

[thekeys93]

Awesome! Thanks for all your help in the countless reviews.

I'll have a follow-up PR out later today.