Add an API to allow _any_ command to be pinned

src/modules/cmdpal/doc/initial-sdk-spec/initial-sdk-spec.md

@@ -2061,6 +2061,7 @@ bands via the new `DockBand` property on `ICommandProvider3`.
 interface ICommandProvider3 requires ICommandProvider2
 {
     ICommandItem[] GetDockBands();
+    ICommandItem GetCommandItemById(String id);
 };
 ```
 

src/modules/cmdpal/ext/Microsoft.CmdPal.Ext.Apps/AllAppsCommandProvider.cs

@@ -188,4 +188,14 @@ public partial class AllAppsCommandProvider : CommandProvider
     {
         RaiseItemsChanged(0);
     }
+
+    public override ICommandItem? GetCommandItemById(string id)
+    {
+        if (id == _listItem.Command.Id)
+        {
+            return _listItem;
+        }
+
+        return _page.GetAppCommandItemById(id);
+    }
 }

src/modules/cmdpal/ext/Microsoft.CmdPal.Ext.Apps/AllAppsPage.cs

@@ -205,4 +205,19 @@ public sealed partial class AllAppsPage : ListPage
 
         RaiseItemsChanged(0);
     }
+
+    internal ICommandItem? GetAppCommandItemById(string id)
+    {
+        var items = this.GetItems();
+
+        foreach (var item in items)
+        {
+            if (item.Command.Id == id)
+            {
+                return item;
+            }
+        }
+
+        return null;
+    }
 }

src/modules/cmdpal/extensionsdk/Microsoft.CommandPalette.Extensions.Toolkit/CommandProvider.cs

@@ -56,6 +56,11 @@ public abstract partial class CommandProvider :
         return null;
     }
 
+    public virtual ICommandItem? GetCommandItemById(string id)
+    {
+        return null;
+    }
+
     /// <summary>
     /// This is used to manually populate the WinRT type cache in CmdPal with
     /// any interfaces that might not follow a straight linear path of requires.