Add logos(crate = "...") attribute

[jannik4]

Add a crate attribute similiar to what serde has.

This allows logos proc-macro to be used and re-exported from another proc-macro without requiring the user to have logos in scope.

[maciejhirsz]

Cheers!

Edit: FYI, gonna change it to use raw path instead of a string, it's easier to parse and provides better errors:

logos/tests/tests/crate_.rs

Line 11 in c6ca58d

#[logos(crate = some::path::_logos)]

[maciejhirsz]

Released in 0.13