Frontmatter and cargo-script

[joshtriplett]

Documentation for frontmatter and cargo-script, as it pertains to the language reference. rust-lang/rust#136889

[epage]

To clarify, this should only be documenting frontmatter as cargo is out of scope for the reference, right?

[joshtriplett]

@epage At least at the moment, I'd expect the behavior of cargo to be out of scope. However, I think documentation of frontmatter would want to give context on what it's used for (and tie it in to whatever the reference currently says about shebangs), so it would make sense to mention its use for cargo-script in that it may be used for a Cargo.toml manifest.

[epage]

rust-lang/reference#1974 says

Frontmatter is an optional section for content intended for external tools without requiring these tools to have full knowledge of the Rust grammar.

Open to the idea of providing a concrete example if thats wanted