Go deep and sketch a bit of content into macro guidelines

Work according to the goals outlined in rustfoundation/safety-critical-rust-coding-guidelines#6 

Fill in five guidelines

DRI: @PLeVasseur 

### Reference material

[The Little Book of Rust Macros](https://veykril.github.io/tlborm/introduction.html)

[Ferrocene Language Specification: Macros](https://spec.ferrocene.dev/macros.html#)