feat: add Chargeable and Refuelable interfaces

src/main/java/org/example/behavior/Chargeable.java

@@ -0,0 +1,5 @@
+package org.example.behavior;
+
+public interface Chargeable {
+    void charge(double amount);
+}

src/main/java/org/example/behavior/Refuelable.java

@@ -0,0 +1,5 @@
+package org.example.behavior;
+
+public interface Refuelable {
+    void refuel(double amount);
+}

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

@@ -11,7 +11,9 @@ package org.example.model;
  *     Reset chargeLevel to 100
  */
 
-public class ElectricCar extends Car {
+import org.example.behavior.Chargeable;
+
+public class ElectricCar extends Car implements Chargeable {
 
     private int batteryCapacity;
     private double chargeLevel;

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

@@ -11,7 +11,9 @@ package org.example.model;
  *     Reset fuelLevel to 100
  */
 
-public class GasCar extends Car {
+import org.example.behavior.Refuelable;
+
+public class GasCar extends Car implements Refuelable {
 
     private double fuelLevel;
     private String fuelType;