add methods GetCharacters() (not finished)

OwnChar/Manager/CharacterManager.cs

@@ -1,7 +1,19 @@
-namespace OwnChar.Manager
+using OwnChar.Model;
+
+namespace OwnChar.Manager
 {
     public class CharacterManager(OwnCharManager manager)
     {
         public OwnCharManager Manager { get; } = manager;
+
+        public IEnumerable<Character>? GetCharacters(Group? group)
+        {
+            throw new NotImplementedException();
+        }
+
+        public IEnumerable<Character>? GetCharacters(Character? character)
+        {
+            throw new NotImplementedException();
+        }
     }
 }