Add project files.

RPGLibrary.Implementation/Character.cs

@@ -0,0 +1,31 @@
+using RPGLibrary.Abstraction.Character;
+
+namespace RPGLibrary.Implementation
+{
+  public class Character : ICharacter
+  {
+    public Character(string name, HP hp, StrengthAttribute strength, DefenseAttribute defense)
+    {
+      Name = name;
+      HP = hp;
+      Strength = strength;
+      Defense = defense;
+    }
+
+    public string Name { get; }
+
+    public HP HP { get; private set; }
+
+    public StrengthAttribute Strength { get; }
+
+    public DefenseAttribute Defense { get; }
+
+    public override string? ToString()
+    {
+      return $"{HP}, {Strength}, {Defense}";
+    }
+
+    public ICharacter With(HP hp) => new Character(Name, hp, Strength, Defense);
+  }
+
+}