Extract LSCOLORS settings into own functions

[andrewwoods]

Description

The LSCOLORS variable determines the color combinations of foreground and background color used for different types of files when running the ls command.

Expected Outcome

Extract different LSCOLORS settings into separate functions, each with a good and clear name, so they can be reused. opal:lscolors_dark_warm

Describe alternatives you've considered

A clear and concise description of any alternative solutions or features you've considered.

Additional Information

Provide a mapping of Letters -> Color primarily has a comment, but additionally on the future documentation site.