Replace cargo-cranky with workspace lints (#4413)

Replace `cargo-cranky` (which has served us well) with workspace lints

examples/custom_keypad/src/main.rs

@@ -1,4 +1,5 @@
 // #![cfg_attr(not(debug_assertions), windows_subsystem = "windows")] // hide console window on Windows in release
+#![allow(rustdoc::missing_crate_level_docs)] // it's an example
 use eframe::egui;
 
 mod keypad;