Encode an index of a nibble from a u64 as a u8.

| 4 bits | 4 bits |

| index of nibble | nibble of data |

# Usage

```rust use crate::CrumbExt;

fn main() { let test: u64 = 0b11111111; // let crumb: u8 = unsafe { test.getuncheckedcrumb(1) }; let crumb: u8 = test.getcrumb(1).unwrap(); asserteq!(0b11110000u64, u64::from_crumb(crumb)); } ```

### Name

A nibble of something is about the size of a crumb or something like that...

### How?

Was doing some research on variable length integers and realized how nicely this fits.

### Why?

I don't think there are too many applications for this, I have one in mind but that is an entire project in itself.