Fix main page example 'Breakout' to 'breakout'

[dscain]

This PR fixes a typo in the Quickstart of README.md.

If one follows the README.md example below in Linux:

from ale_py import ALEInterface, roms

ale = ALEInterface()
x = roms.get_rom_path("Breakout")
ale.loadROM(x)
ale.reset_game()

reward = ale.act(0)  # noop
screen_obs = ale.getScreenRGB()

you get UserWarning: Rom Breakout not supported. and get_rom_path returns None and then

TypeError: loadROM(): incompatible function arguments. The following argument types are supported:
    1. (self: ale_py._ale_py.ALEInterface, arg0: str) -> None
    2. (self: ale_py._ale_py.ALEInterface, arg0: os.PathLike) -> None

The issue is the file search is case sensitive. To fix, just run the same with breakout instead of Breakout.

[pseudo-rnd-thoughts]

Thanks for spotting this