add solution

src/herbivoresAndCarnivores.js

@@ -2,14 +2,43 @@
 
 class Animal {
   // write your code here
+  static alive = [];
+
+  constructor(name) {
+    this.name = name;
+    this._health = 100;
+    Animal.alive.push(this);
+  }
+
+  get health() {
+    return this._health;
+  }
+
+  set health(value) {
+    this._health = value;
+
+    if (this._health <= 0) {
+      Animal.alive = Animal.alive.filter((animal) => animal.health > 0);
+    }
+  }
 }
 
 class Herbivore extends Animal {
   // write your code here
+  hidden = false;
+
+  hide() {
+    this.hidden = true;
+  }
 }
 
 class Carnivore extends Animal {
   // write your code here
+  bite(herbivore) {
+    if (herbivore instanceof Herbivore && !herbivore.hidden) {
+      herbivore.health -= 50;
+    }
+  }
 }
 
 module.exports = {