Make draw_character() and character_advance() available to users

[bbogdan-ov]

Hi! I'm writing a custom text input, so i need to constantly calculate the size of the text that user enters

Using basic draw_text() and measure_text() may be quite slow, because it calculates the size for the whole text.
I used slices to calculate the size of the string/text from the beginning to the cursor position, but it also slows down my game!

I want to implement something like this in text.rs module:

// May be called like `CharacterDimensions`
pub struct CharDimensions {
    width: f32,
    offset_y: f32
}

/// Draws the character and returns its size
pub fn draw_character(character: char, x: f32, y: f32, font: Option<&Font>, font_size: u16, color: Color) -> CharDimensions;
/// Returns the character size
pub fn measure_character(character: char, font: Option<&Font>, font_size: u16) -> CharDimensions;

Also i would like draw_text() and draw_text_ex() to return TextDimensions, because they have already been calculated, so we don't need to recalculate them again

Want to hear what you think about it :)