Updates for egui 0.28

[Resonanz]

The following compiles and runs fine.

cargo.toml:

[dependencies]
egui26 = { version = "0.26", package = "egui", default-features = false, optional = true }
egui27 = { version = "0.27", package = "egui", default-features = false, optional = true }
egui28 = { version = "0.28", package = "egui", default-features = false, optional = true }

[dev-dependencies]
eframe = "0.28"

[features]
default = ["egui28"]

Line 11 of todo.rs:

if let Err(e) = eframe::run_native("todos", native_options, Box::new(|_| Ok(Box::new(app)))) {

lib.rs, lines 33 onwards:

#[cfg(not(any(feature = "egui26", feature = "egui27", feature = "egui28")))]
compile_error!("at least one egui version must be enabled");

#[cfg(feature = "egui26")]
use egui26 as egui;
#[cfg(feature = "egui27")]
use egui27 as egui;
#[cfg(feature = "egui28")]
use egui28 as egui;