Extend compiler and clippy lints

[robin-nitrokey]

E. g. in opcard we use this configuration:

#![warn(
    missing_copy_implementations,
    missing_debug_implementations,
    missing_docs,
    non_ascii_idents,
    trivial_casts,
    unused,
    unused_qualifications,
    clippy::expect_used,
    clippy::unwrap_used
)]
#![deny(unsafe_code)]

https://github.com/Nitrokey/opcard-rs/blob/main/src/lib.rs#L31-L42

Exceptions that require e. g. unwrap can be whitelisted explicitly:

#[allow(clippy::unwrap_used)]
some_function().unwrap();  // always ok because of ...

[szszszsz]

Fixed in #75