Use without bevy

[tversteeg]

Would it be possible to make the integration with bevy an optional feature? I would love to use this in my own game engine, and I think the Rust ecosystem as a whole can benefit from a solution like this.

[alice-i-cecile]

Yeah, I was wondering if others would find this useful :) #21 was an attempt at this: if you'd like, I'd be happy to review a PR that revived it!