feat: añadido listar repositorio

Modelo/Modelo.sln

@@ -0,0 +1,25 @@
+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.5.002.0
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Modelo", "Modelo.csproj", "{332ACC5A-D3E1-4E7A-A363-BDC1CB370350}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{332ACC5A-D3E1-4E7A-A363-BDC1CB370350}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{332ACC5A-D3E1-4E7A-A363-BDC1CB370350}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{332ACC5A-D3E1-4E7A-A363-BDC1CB370350}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{332ACC5A-D3E1-4E7A-A363-BDC1CB370350}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {DFA3F249-7A0D-474C-A190-5C2E568DFB1C}
+	EndGlobalSection
+EndGlobal

Modelo/RepositorioBase.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.ObjectModel;
 
 namespace Modelo
 {
@@ -24,6 +25,11 @@ namespace Modelo
             }   
         }
 
+        // Lista el contenido del repositorio
+        public ReadOnlyCollection<T> Listar(){
+            return almacen.AsReadOnly();
+        }
+
         // Añade objetos al almacen
         abstract public bool Add(T t);