Add arguments to deriving traits

[riberk]

#[derive(Embed)]
#[path = "../", dir(derive(Sha2(256)))]
pub struct Assets;

But for custom things, like Blake3(658), it requires to generate traits, instead of to use existing.

That's something to think about.

[riberk]

With type-safety, it might be something like this

// lib-defined
pub trait Blake3HashSelector {
    type Tag;
    fn select_blake3(&self, tag: Self::Tag) -> &'static [u8];
    fn select_blake3_by_bits(&self, bits: usize) ->Option< &'static [u8]>;
}

// lib-defined
pub trait Blake3Hash<const B: usize> {
    fn blake3(&self) -> &'static [u8; B];
}

// auto-generated
pub enum AssetsBlake3Tag {
    H256,
    H512,
    H1024,
}

// auto-generated
impl AssetsBlake3Tag {
    pub fn select<T: Blake3Hash<32> + Blake3Hash<64> + Blake3Hash<128>>(&self, provider: &T) -> &'static [u8] {
        match self {
            Self::H256 => Blake3Hash::<32>::blake3(provider),
            Self::H512 => Blake3Hash::<64>::blake3(provider),
            Self::H1024 => Blake3Hash::<128>::blake3(provider),
        }
    }
}
// auto-generated
pub trait Dir: Blake3HashSelector<Tag = AssetsBlake3Tag> + Blake3Hash<32>  + Blake3Hash<64>  + Blake3Hash<128>{

}
// user-defined
pub struct Assets;

// auto-generated
impl Blake3Hash<32> for Assets {
    fn blake3(&self) -> &'static [u8; 32] {
        todo!()
    }
}
// auto-generated
impl Blake3Hash<64> for Assets {
    fn blake3(&self) -> &'static [u8; 64] {
        todo!()
    }
}
// auto-generated
impl Blake3Hash<128> for Assets {
    fn blake3(&self) -> &'static [u8; 128] {
        todo!()
    }
}
// auto-generated
impl Blake3HashSelector for Assets {
    type Tag = AssetsBlake3Tag;
    
    fn select_blake3(&self, bits: AssetsBlake3Tag) -> &'static [u8] {
        bits.select(self)
    }
}