Encode an index of a [nibble](https://en.wikipedia.org/wiki/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.get_unchecked_crumb(1) };
let crumb: u8 = test.get_crumb(1).unwrap();
assert_eq!(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.