Enable debugging of SmallSharp tasks via MSBuild property

Set DebugSmallSharp=true to get a debugger launched when
SmallSharp is about to start VS integration.

Author: kzu

src/SmallSharp/MonitorActiveDocument.cs

@@ -18,8 +18,15 @@ public class MonitorActiveDocument : Task
     [Required]
     public ITaskItem[] StartupFiles { get; set; } = Array.Empty<ITaskItem>();
 
+    public string? Debugger { get; set; }
+
     public override bool Execute()
     {
+        if (bool.TryParse(Debugger, out var debugger) && debugger)
+        {
+            System.Diagnostics.Debugger.Launch();
+        }
+
         if (string.IsNullOrEmpty(LaunchProfiles) ||
             string.IsNullOrEmpty(UserFile))
         {

src/SmallSharp/SmallSharp.targets

@@ -30,7 +30,8 @@
   <Target Name="MonitorActiveDocument" Condition="'$(BuildingInsideVisualStudio)' == 'true'" AfterTargets="CompileDesignTime" DependsOnTargets="CollectStartupFile">
     <MonitorActiveDocument LaunchProfiles="$([System.IO.Path]::Combine('$(MSBuildProjectDirectory)', 'Properties', 'launchSettings.json'))"
                            UserFile="$([System.IO.Path]::Combine('$(MSBuildProjectDirectory)', '$(MSBuildProjectFile).user'))"
-                           StartupFiles="@(StartupFile)" />
+                           StartupFiles="@(StartupFile)"
+                           Debugger="$(DebugSmallSharp)"/>
   </Target>
 
   <Target Name="StartupFile" BeforeTargets="BeforeCompile;CoreCompile;CompileDesignTime" DependsOnTargets="$(StartupFileDependsOn)" />