Honor scale in FlxBitmapText width and height, add setCharFrame

[Geokureli]

1. Adds setCharFrame to allow the adjustment of char frames after it's created, all the methods in FlxBitmapFont are private making it hard to make custom fonts via code, example, currently I have the following code in a project:

static function createFont()
{
	final font = FlxBitmapFont.fromMonospace(AssetPaths.font__png, "", new FlxPoint(8, 8));
	
	final chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ!";
	final widths = ['I'.code=>3, '!'.code=>3, 'T'.code=>7];
	var x:Int = 0;
	for (i in 0...chars.length)
	{
		final charCode = chars.charCodeAt(i);
		final width = widths.exists(charCode) ? widths[charCode] : 8;
		final frame = FlxRect.get(x, 0, width, 8);
		@:privateAccess
		font.addCharFrame(charCode, frame, FlxPoint.weak(), width);
		x += width;
	}
	return font;
}

I shouldn't need to use @:privateAccess to adjust a few chars. We could add a new arg to fromMonospace (or make a new func) that takes a map of widths and a default width, but we should really expose some of these methods, anyway

2. when you scale up a bitmap text and call updateHitbox the width/height is set to the correct value, but anytime you change something it gets set back to the frameWidth/frameHeight. This will honor scale whenever it sets width and height. Ideally it shouldn't set width and height ever, only frameWidth and frameHeight because w/h are used for collision but thats an old ass problem I don't want to fix now