Add optional `view` argument to `Window.run()' and `arcade.run()`

[DragonMoffon]

To help promote subclassing views over the window itself, we should add an optional view argument to the run methods, letting them automatically call Window.show_view.

It results in only a one-line change, but it makes the DX (Developer Experice) nicer.

It will also need a unit test for each method, and the examples will need updating to take advantage of the change.

[joaomarcalst]

I’ve submitted a pull request to add the optional view argument to Window.run() as discussed. While implementing, I encountered some issues with pyglet that prevented complete testing, but the initial functionality is in place. Let me know if any adjustments are needed!