allow public uses of structs; add sample program

src/sprite.rs

@@ -2,12 +2,12 @@ use crate::{AnimationFrames, Image, Position, mock};
 
 #[derive(Debug, Eq, PartialEq)]
 pub struct Sprite {
-    pub(crate) id: String, // lowercase base36
-    pub(crate) name: Option<String>,
-    pub(crate) animation_frames: Vec<Image>,
-    pub(crate) dialogue: Option<String>, /// dialogue id
-    pub(crate) room: String, /// room id
-    pub(crate) position: Position,
+    pub id: String, // lowercase base36
+    pub name: Option<String>,
+    pub animation_frames: Vec<Image>,
+    pub dialogue: Option<String>, /// dialogue id
+    pub room: String, /// room id
+    pub position: Position,
 }
 
 impl From<String> for Sprite {