Upgrade to Bevy 0.16

[rparrett]

Fixes #3

Bevy has built-in entity cloning now, so we can delete a bunch of code! Neat.

There probably won't be a crates.io release until Bevy 0.16.0 is properly released, but you can use this git branch in the mean time.

[dependencies.bevy_simple_rich_text]
git = "https://github.com/rparrett/bevy_simple_rich_text.git"
branch = "bevy-0.16"