[feature] Inline formatting for percentages

[tzakharko]

I find myself frequently reporting proportions as percentages, so it would be nice if cli supported a .percent formatter out of the box. @gaborcsardi would it be ok if I submitted a pull request for this?

[gaborcsardi]

Thanks! Ideally we would have a (better) way for people to define their own formatters, instead of putting everything in cli.

Also, for percentages, you can use the scales package, or define your own simple function that does the formatting, and call it from the format string:

pct <- scales::label_percent()
n <- .65
cli::cli_text("{pct(n)} percent of percentages are larger than {pct(.5)}.")

#> 65% percent of percentages are larger than 50%.