add documentation

battlesnake/src/main.rs

@@ -30,7 +30,9 @@ pub enum Direction {
 
 #[derive(Debug, Deserialize, Serialize)]
 pub struct Move {
+    /// In which direction the snake should move
     r#move: Direction,
+    /// Say something to the other snakes
     #[serde(default, skip_serializing_if = "is_default")]
     shout: Option<String>,
 }