Add plugin isolation IPC scaffolding and host phase one docs

LanMountainDesktop.PluginSdk/PluginWorkerBase.cs

@@ -0,0 +1,20 @@
+using Microsoft.Extensions.DependencyInjection;
+
+namespace LanMountainDesktop.PluginSdk;
+
+public abstract class PluginWorkerBase : IPluginWorker
+{
+    public virtual void ConfigureServices(IPluginWorkerContext context, IServiceCollection services)
+    {
+    }
+
+    public virtual Task StartAsync(IPluginWorkerContext context, IServiceProvider services, CancellationToken cancellationToken = default)
+    {
+        return Task.CompletedTask;
+    }
+
+    public virtual Task StopAsync(CancellationToken cancellationToken = default)
+    {
+        return Task.CompletedTask;
+    }
+}