Function draw_text_centered 

pub fn draw_text_centered(
    buf: &mut [u8],
    buf_w: i32,
    buf_h: i32,
    y0: i32,
    text: &str,
    color: [u8; 3],
    window_alpha: f32,
    bgr: bool,
)

Horizontally-centered draw_text at row y0.