Add level names

src/levels/mod.rs

@@ -40,6 +40,14 @@ impl Difficulty {
             Self::Hard => "Hard (95%)",
         }
     }
+
+    pub fn name(self) -> &'static str {
+        match self {
+            Self::Easy => "Easy",
+            Self::Medium => "Medium",
+            Self::Hard => "Hard",
+        }
+    }
 }
 
 /// What `Level::generate` returns: the canonical target YAML to grade