Support for try_into instead of into

[andreasWallnerIFX]

If I understand the current API correctly we can do conversion of bitfield fields via specifying into T in the field specification. What I'm currently missing is a way to use try_into instead of into.

With my use-case it would look like this (in our normal case I'd use num_enum, removed that for simplicity):

#[repr(u8)]
pub enum UidSize {
    Single = 0,
    Double = 1,
    Triple = 2,
}
impl TryFrom<u8> for UidSize {
    type Error = ();

    fn try_from(value: u8) -> Result<Self, Self::Error> {
        match value {
            0 => Ok(UidSize::Single),
            1 => Ok(UidSize::Double),
            2 => Ok(UidSize::Triple),
            _ => Err(()),
        }
    }
}

bitfield! {
  pub struct Atqa(u16);
  impl Debug;
  // The fields default to u16
  pub bitframe_anticoll, set_bitframe_anticoll: 4, 0;
  pub u8, from try_into UidSize, uid_size, set_uid_size: 7, 6;
}

and the uid_size getter would have to have a Result<UidSize, ()> return value.

Is this currently possible and I overlooked it? Otherwise it would be cool if this could be added...