Add #![forbid(unsafe_code)] where unsafe isn't needed (#2773)

To be consistent with the use of the safety badge in the README.

crates/egui/src/lib.rs

@@ -298,6 +298,7 @@
 
 #![allow(clippy::float_cmp)]
 #![allow(clippy::manual_range_contains)]
+#![forbid(unsafe_code)]
 
 mod animation_manager;
 pub mod containers;

crates/egui_demo_lib/src/lib.rs

@@ -10,6 +10,7 @@
 
 #![allow(clippy::float_cmp)]
 #![allow(clippy::manual_range_contains)]
+#![forbid(unsafe_code)]
 
 mod color_test;
 mod demo;

crates/egui_extras/src/lib.rs

@@ -8,6 +8,7 @@
 
 #![allow(clippy::float_cmp)]
 #![allow(clippy::manual_range_contains)]
+#![forbid(unsafe_code)]
 
 #[cfg(feature = "chrono")]
 mod datepicker;

crates/egui_glium/src/lib.rs

@@ -10,6 +10,7 @@
 
 #![allow(clippy::float_cmp)]
 #![allow(clippy::manual_range_contains)]
+#![forbid(unsafe_code)]
 
 mod painter;
 pub use painter::Painter;

crates/emath/src/lib.rs

@@ -20,6 +20,7 @@
 //!
 
 #![allow(clippy::float_cmp)]
+#![forbid(unsafe_code)]
 
 use std::ops::{Add, Div, Mul, RangeInclusive, Sub};
 

crates/epaint/src/lib.rs

@@ -11,6 +11,7 @@
 
 #![allow(clippy::float_cmp)]
 #![allow(clippy::manual_range_contains)]
+#![forbid(unsafe_code)]
 
 mod bezier;
 pub mod image;