Updated for bevy-0.5

[brianbruggeman]

Primarily updates to be compatible with bevy 0.5, but also:

• Updates for IDE file ignores
• Added a Makefile for development workflow convenience
• Added a .rustfmt file and ran rustfmt
• Bumped bevy_crossterm version to 0.5
• Migrated package uses from within the code up to the top of the code for visibility
• Used clippy suggestions
• Migrated lib.rs structures into their own files

Two logic changes that I think are relevant here.

1. The changes within bevy-0.5 for pipeline stages allows for all of the stages to be executed within a single frame. Previously, we expected only one stage to be executed within a frame. The consequence is that it's less clear how state transitions actually run and also how to handle capturing input from the user. The API appears to have the right pieces, but the execution is no longer simple/intuitive.

2. Because of the changes, we now explicitly update the keys data within the user input handler and we also initiate a cleanup within the same code space because it appears that the on_exit method is actually completely broken for state transitions. I have let the on_exit methods in there mostly because I think they should work. However, I've commented them out because they do not actually appear to run as expected.

Fixes #7