Consider normalising pygambit level spacing options

[edwardchalstrey1]

Requested enahancement or feature

Currently in draw_tree we have the following args in draw_tree within src/draw_tree/core.py:

def draw_tree(
    game: str | "pygambit.gambit.Game",
    save_to: Optional[str] = None,
    scale_factor: float = 0.8,
    level_spacing: int = 4,
    sublevel_spacing: int = 2,
    width_spacing: int = 2,
    show_grid: bool = False,
) -> Optional[str]:

The level_spacing, sublevel_spacing and width_spacing args are used when the game is a pygambit.gambit.Game as a way of determining how Gambit's own layout algorithm gets converted to .ef format (see src/draw_tree/gambit_layout.py.

It may be worth updating how this works so you can pass a value between 0 and 1 to draw_tree similar to how scale_factor works.