feat: add showDetails feature to vehicle

src/main/java/org/example/model/GasCar.java

@@ -30,4 +30,6 @@ public class GasCar extends Car {
     // TODO: Implement refuel(double amount)
     // Validate amount
     // Cap at 100
+
+    // TODO: Override showDetails()
 }

src/main/java/org/example/model/Vehicle.java

@@ -35,4 +35,6 @@ public abstract class Vehicle {
                         " | Energy: " + getEnergyType()
         );
     }
+
+    public abstract void showDetails();
 }