review: change roll result type to i32

01.workspace/oxidice_lib/src/imp/die_roll.rs

@@ -1,8 +1,8 @@
 use crate::*;
 
 impl Die {
-    pub fn roll(&self) -> u16 {
+    pub fn roll(&self) -> i32 {
         let mut rng = rand::rng();
-        rng.random_range(1..=self.sides) as u16
+        rng.random_range(1..=self.sides) as i32
     }
 }