Added system iterator

crates/content/src/lib.rs

@@ -272,6 +272,11 @@ impl Content {
 
 // Access methods
 impl Content {
+	/// Iterate over all valid system handles
+	pub fn iter_systems(&self) -> impl Iterator<Item = SystemHandle> {
+		(0..self.systems.len()).map(|x| SystemHandle { index: x })
+	}
+
 	/// Get the handle for the starfield sprite
 	pub fn get_starfield_handle(&self) -> SpriteHandle {
 		match self.starfield_handle {