Bumped bevy_egui to 0.26 in egui backend

[Mat-Stevenson-Simworx]

Bumped bevy_egui to 0.26. Fixes dependency issue when using bevy_egui 0.26 in project.

[Zoomulator]

bevy_egui just released 0.27
I noticed picking stopped working for bevy-inspector-egui latest release which uses bevy_egui 0.27

[aevyrie]

At this point we might need to add explicit version features, like bevy_egui_0_25, bevy_egui_0_26, and bevy_egui_0_27, so we don't force users to update egui to get the latest mod_picking bugfixes.

We can change the default version to be the latest when using the bevy_egui feature (with no version on the end), but give users the ability to pick and choose which compatible version of bevy_egui they want to use for any version of mod_picking.

[aevyrie]

TIL you can specify a dep as a range of versions. Opening a PR.

[aevyrie]

Closing in favor of #334