Document this library

[TomAFrench]

There's zero in the way of proper documentation here. Trivial example but what's the difference between these two functions? They're just variants 1 and 2...

noir_bigcurve/src/scalar_field.nr

Lines 23 to 69 in c36268d

	unconstrained fn get_wnaf_slices<let N: u32>(x: Field) -> ([u8; N], bool) {
	let mut result: [u8; N] = [0; N];
	let mut nibbles = x.to_le_radix::<N>(16);
	let skew: bool = nibbles[0] & 1 == 0;
	nibbles[0] = nibbles[0] as u8 + (skew as u8);
	result[N - 1] = (nibbles[0] + 15) / 2;
	for i in 1..N {
	let mut nibble: u8 = nibbles[i];
	result[N - 1 - i] = (nibble + 15) / 2;
	if (nibble & 1 == 0) {
	result[N - 1 - i] += 1;
	result[N - i] -= 8;
	}
	}
	(result, skew)
	}
	unconstrained fn get_wnaf_slices2<let N: u32, BigNum>(x: BigNum) -> ([u8; N], bool)
	where
	BigNum: BigNumTrait,
	{
	let mut result: [u8; N] = [0; N];
	let mut nibbles: [[u8; 30]; (N / 30) + 1] = [[0; 30]; (N / 30) + 1];
	let x: [Field] = x.get_limbs_slice();
	for i in 0..x.len() {
	nibbles[i] = x[i].to_le_radix::<30>(16);
	}
	let skew: bool = nibbles[0][0] & 1 == 0;
	nibbles[0][0] = nibbles[0][0] as u8 + (skew as u8);
	result[N - 1] = (nibbles[0][0] + 15) / 2;
	for i in 1..N {
	let major_index = i / 30;
	let minor_index = i % 30;
	let mut nibble: u8 = nibbles[major_index][minor_index];
	result[N - 1 - i] = (nibble + 15) / 2;
	if (nibble & 1 == 0) {
	result[N - 1 - i] += 1;
	result[N - i] -= 8;
	}
	}
	(result, skew)
	}

We have CurveJ and BigCurve, what's the difference between these from a consumer's point of view, etc.

We should have proper doc comments on the implementation of this library to make it clearer for maintainers and users what's going on in this library.