Function format_bar_chart 

pub fn format_bar_chart(
    label: &str,
    count: usize,
    fraction: f64,
    unit: &str,
    color: bool,
) -> String

Format a horizontal bar chart entry.

Produces: ▓▓▓▓▓▓▓░░░░░░░░░░░░░ 34.5% Rust (42 files)

fraction should be in 0.0..=1.0.