Add rustfmt

[Sirmadeira]

I believe adding a rustfmt file, to make the imports pretty. Would be a great addition to simplify import maintenance.
imports_granularity = "Crate"
group_imports = "StdExternalCrate"

[cBournhonesque]

Thoes require nightly though, right?
(just from looking at bevy: https://github.com/bevyengine/bevy/blob/main/rustfmt.toml#L7)

[Sirmadeira]

It does yes. In general I believe, that also getting rid of the allow x warnings via workspaces lints. Would also be a general improvement.