TODO

alternative source apis
    add to readme
    add arg docs

overhaul error handling
    difference between cloudflare 429 vs other 429?
    document variants
    rename variants

use mpsc to send error to main?

(chores)
    document public items
    readme
        make better
    linting
        standardize `use` statement order
    refactor and clean up modules
        too many items in `lib.rs`

add tests
    unit test simple functions
    integration test

perf: save raw bytes to file, instead of converting to image, when saving as .gif
    this might be a little annoying to change

refactor: does `date_to_string` need `leading_zeros` parameter?
    can be removed if gocomics accepts leading zeros
    maybe just replace with manual `format!`