Constructs a validated style object for use with table_default().
Examples
td_style(mpg = "cyan", cyl = "magenta")
#> <tabstats_style / td_style>
#> mpg: "cyan"
#> cyl: "magenta"
td_style(mpg = \(ctx) cli::col_red(ctx$value), title = "bold")
#> <tabstats_style / td_style>
#> mpg: <function>
#> title: "bold"
