Update egui and glam

[Azkellas]

Thank you for this great crate. :)

[Azkellas]

I realised after the first draft that the demo uses bevy and bevy_egui. bevy_egui supports egui 0.27 upstream but not yet on crates.io so I switched to a git rev dependency temporarily. bevy_egui maintainer said they would update soon so I guess we can wait for their update first if you wish to avoid another git dependency.

[urholaukkarinen]

Thanks for the pull request! Some pretty big changes are coming, which also include the updated dependency versions.