Hello!

Could you please add license information into Cargo.toml file, as it described here https://doc.rust-lang.org/cargo/reference/manifest.html#the-license-and-license-file-fields ?

Also it would be great to copy the text of license into separate file, like LICENSE.txt, so for example GitHub will recognise it.

I found your project from a fork https://github.com/pcein/rust-sipeed-longan-nano which has no license information at all, probably because README file was rewritten.