enable find to be able to highlight some hits

[fdncred]

Description

This change enables the find command to be able to highlight hits in certain circumstances. Everything should work the same as it used to with the exception of ls | find term1 term2 term3 should now be highlighted with white on red.

There are some corner cases that this find change and the original help highlighting change fail on.

• If what you're highlighting is not a string, it will color everything except the highlighted portions as the string color defined in your config.
• if you have use_ls_colors set to true and you happen to be finding on items that look like file names, the file names may be colored as ls_colors colored them except for the highlighted portion

TODOS - up for grabs

• find doesn't highlight on anything but tables as in the example. please feel free to contribute highlighting on strings and lists.
• allow help -f and find to use a custom_highlight_color instead of always using white on red

This PR also contains a small refactor to LS_COLORS so we don't have to copy that default LS_COLORS env var string around everywhere.

Tests

Make sure you've done the following:

• Add tests that cover your changes, either in the command examples, the crate/tests folder, or in the /tests folder.
• Try to think about corner cases and various ways how your changes could break. Cover them with tests.
• If adding tests is not possible, please document in the PR body a minimal example with steps on how to reproduce so one can verify your change works.

Make sure you've run and fixed any issues with these commands:

• cargo fmt --all -- --check to check standard code formatting (cargo fmt --all applies these changes)
• cargo clippy --workspace --features=extra -- -D warnings -D clippy::unwrap_used -A clippy::needless_collect to check that you're using the standard code style
• cargo test --workspace --features=extra to check that all the tests pass