add a simple plugin system

Pilz.Plugins.Advanced/PluginModuleController.cs

@@ -0,0 +1,29 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Z.Collections.Extensions;
+
+namespace Pilz.Plugins.Advanced
+{
+    public sealed class PluginModuleController
+    {
+        public static PluginModuleController Instance { get; private set; } = new();
+
+        private readonly List<PluginModule> modules = new();
+
+        public IReadOnlyList<PluginModule> Modules => modules.AsReadOnly();
+
+        public void RegisterModule(PluginModule module)
+        {
+            if (!modules.Contains(module))
+                modules.Add(module);
+        }
+
+        public void UnregisterModule(PluginModule module)
+        {
+            modules.Remove(module);
+        }
+    }
+}