* Enable using color palettes in theme files.
* Add an example theme defined using a gruvbox color palette.
* Fix clippy error.
* Small style improvement.
* Add documentation for the features to themes.md.
* Update runtime/themes/gruvbox.toml
Fix the value of purple0.
Co-authored-by: DrZingo <DrZingo@users.noreply.github.com>
Co-authored-by: DrZingo <DrZingo@users.noreply.github.com>