TODO

*- REFACTOR: Remove qualifiers from namespaced constants: CODE39_CHARS -> CHARS.
*- FEATURE: Code11 symbology
*.- PERFORMANCE: If checksum_char functions were private, it would allow for them to return the encoding instead of the char and thus the extra lookup to char_encoding would be able to be skipped (see Code39, etc)
*  - REFACTOR: Perhaps make them all private and behave the same? (code128 returns u8, code39 returns char. wtf?)
*- REFACTOR: Fix monstrosity in place_pixels in image generator. (Potentially write a simple macro?)
- PERFORMANCE: If user doesn't set image color, default to Luma8 instead of Rgba8 to save bytes.
- REFACTOR: Implement simple regex into Parse and remove valid_chars, valid_length, etc.