cli_unicode_option: whether the cli.unicode option is set and its
value. See is_utf8_output().
symbol_charset: the selected character set for symbol, UTF-8,
Windows, or ASCII.
console_utf8: whether the console supports UTF-8. See
base::l10n_info().
latex_active: whether we are inside knitr, creating a LaTeX
document.
num_colors: number of ANSI colors. See num_ansi_colors().
console_with: detected console width.