Use ~~miette~~ annotate-snippets for reporting errors from invalid `Cargo.toml`s

[eopb]

https://docs.rs/miette/latest/miette/

https://github.com/rust-lang/annotate-snippets-rs

toml_edit should be able to provide spans we can use: https://docs.rs/toml_edit/latest/toml_edit/?search=span

[eopb]

We don't do much manual parsing anymore, mostly relying on cargo metadata so there's not much point in doing this

[epage]

Do you want to match cargo and use annotate-snippets?

[eopb]

That's better 👍
I've updated the issue description to suggest annotate-snippets