add a simple plugin system

Pilz.Plugins/PluginLoadContext.cs

@@ -0,0 +1,40 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+using System.Runtime.Loader;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Pilz.Plugins
+{
+    internal class PluginLoadContext : AssemblyLoadContext
+    {
+        private readonly AssemblyDependencyResolver _resolver;
+
+        public PluginLoadContext(string pluginPath)
+        {
+            _resolver = new AssemblyDependencyResolver(pluginPath);
+        }
+
+        protected override Assembly? Load(AssemblyName assemblyName)
+        {
+            var assemblyPath = _resolver.ResolveAssemblyToPath(assemblyName);
+
+            if (assemblyPath != null)
+                return LoadFromAssemblyPath(assemblyPath);
+
+            return null;
+        }
+
+        protected override IntPtr LoadUnmanagedDll(string unmanagedDllName)
+        {
+            var libraryPath = _resolver.ResolveUnmanagedDllToPath(unmanagedDllName);
+
+            if (libraryPath != null)
+                return LoadUnmanagedDllFromPath(libraryPath);
+
+            return IntPtr.Zero;
+        }
+    }
+}