Bevy 0.19

[AndreRoelofs]

Hey,

Thanks for creating such a cool project, you helped me solve a challenging issue super nicely!

I did the 0.19 migration, as specified below:

1. Remove Component and Resource derivations from Props according to the migration guide.
2. Create GlobalProps newtype for Props that derives Resource and implements Deref for transparent access to Props.
3. Create EntityProps newtype for Props that derives Component and implements Deref for transparent access to Props.
4. Add simple gitignore
5. Run cargo fmt --all
6. Updated docs to reflect the changes
7. Add simple tests for props to confirm baseline functionality
8. Add a test to check if the code works with the newly released bsn! macro as per some Discord discussion
9. Bump version to 3.0.0 and update related docs.

I am not usually for using Deref on newtypes but I feel like it fits very nicely in this particular case.

The naming for the newtypes was chosen to loosely follow Bevy's example namely

UiDebugOverlay is split into GlobalUiDebugOverlay (resource) and UiDebugOverlay (component)