Configure number of lines between module comments and module attributes

It would be great if I could have an opinionated configuration for if there are lines between module //! Documentation and module #![attributes].

There could be perhaps One, Zero and Preserve.

Example code:

//! Some module documentation.


#![no_std]

With One:

//! Some module documentation.

#![no_std]

With Zero:

//! Some module documentation.
#![no_std]

and with Preserve (probably the default):

//! Some module documentation.


#![no_std]

Would this be possible? Could be a fun weekend PR for me to do as long as it's something the project would accept :)

Thanks!

Start by tracing rustfmt's handling of module documentation and module attributes, then review existing formatting configuration options and tests. Add coverage for One, Zero, and Preserve behavior using the examples in the issue; done means each setting produces the specified spacing.