message: chore(CoordMap): add comments
diff: @@ -55,6 +55,7 @@ pub struct CoordMap {
  }
  impl CoordMap {
  + /// Takes aligned ref_seq before insertions (i.e. gaps in ref) are stripped
  pub fn new(ref_seq: &[Nuc]) -> Self {
  Self {
  aln_to_ref_table: make_aln_to_ref_map(ref_seq),
  @@ -66,6 +67,7 @@ impl CoordMap {
  self.aln_to_ref_table[aln]
  }
  + // Reff is used because `ref` is magic word in Rust
  pub fn ref_to_aln_scalar(&self, reff: usize) -> usize {
  self.ref_to_aln_table[reff]
  }
  