Use `{cli}` package

[trevorld]

• Use {cli} instead of {crayon}
• Support user-customized {cli} color "palettes"
• Document relevant options such as palette options and number of colors
• Use {cli}'s HTML output instead of {fansi}'s
• File HTML conversion bug report upstream to {cli}?

[trevorld]

{cli} HTML conversion bug reported upstream with a minimal, reproducible example: r-lib/cli#752

[trevorld]

We ran into a blocker switching to cli::ansi_html() for HTML output. Even with the ansi_html(ansi_simplify(x)) workaround, the background color is still dropped from subsequent spans whenever only the foreground changes — the same bug that affects ansi_html(x) directly.

Minimal reproducible example:

library(cli)
packageVersion("cli") # 3.6.5

withr::with_options(list(cli.num_colors = 256L), {
  x <- paste0(
    combine_ansi_styles(col_black, bg_br_white)("A"),
    combine_ansi_styles(col_red,   bg_br_white)("B")
  )
  # ESC[107m is explicitly present before B in the raw sequence, but
  # ansi_html() still drops ansi-bg-color-7 from B's span
  cat("HTML (raw):       ", ansi_html(x), "\n")
  cat("HTML (simplified):", ansi_html(ansi_simplify(x)), "\n")
})
# HTML (raw):        <span class="ansi ansi-color-0 ansi-bg-color-7">A</span>
#                    <span class="ansi ansi-color-1">B</span>
# HTML (simplified): <span class="ansi ansi-color-0 ansi-bg-color-7">A</span>
#                    <span class="ansi ansi-color-1">B</span>
#
# Expected both spans to have ansi-bg-color-7

We will stay on fansi::sgr_to_html() until this is fixed.