feat: sort ASCII-style alignment pileups

[deliaBlue]

Modify the ascii_alignment_pileup.R script to return the ASCII-style alignment pileups sorted according to the:

--sort-by: specify the sort type (either "position" or "counts". Default: "position")

--reverse-sort: reverse the sort order (from "from-left-to-right" to "from-right-to-left" for sort type "position" and from "descending" to "ascending" for sort type "counts")

[uniqueg]

Given that you have two separate scripts for the ASCII and HTML generation, I'm tending to think that the ASCII should always produce complete outputs and should not be filtered. Instead, filtering could be applied to the HTML generation. That way, we separate concerns - one script generates the pileups, the other one creates publication-style visualizations from them.