Tidy DEP 14 a bit

[adamchainz]

1. Indent Python code with four spaces, rather than three.
2. Modernize and complete the type hints, specifically replacing Dict and List with dict[k, v] and list (or tuple[Any, ...] in the case of Task.args).
3. Tidy language around asynchronous tasks, including expanding the “async” shorthand and removing its syntax highlighting.
4. Replace the term “globally-importable” with “module-level”, which is what I understood was meant.
5. Use the term “enqueueing” consistently.

[adamchainz]

@RealOrangeOne

[RealOrangeOne]

I have absolutely no idea how the indenting got this messed up, but thanks for cleaning it up!

I also the changed wording is much clearer - thanks again.

[RealOrangeOne]

As you're already here, it'd be great if you could amend #86 (comment) at the same time! 🙂

[adamchainz]

As you're already here, it'd be great if you could amend #86 (comment) at the same time! 🙂

Done, merging!