Add some xmldoc comments

Author: jcansdale

src/GitHub.InlineReviews/PullRequestStatusBarPackage.cs

@@ -15,6 +15,9 @@ namespace GitHub.InlineReviews
     [ProvideAutoLoad(Guids.GitSccProviderId)]
     public class PullRequestStatusBarPackage : AsyncPackage
     {
+        /// <summary>
+        /// Initialize the PR status UI on Visual Studio's status bar.
+        /// </summary>
         protected override async Task InitializeAsync(CancellationToken cancellationToken, IProgress<ServiceProgressData> progress)
         {
             var componentModel = (IComponentModel)await GetServiceAsync(typeof(SComponentModel));

src/GitHub.InlineReviews/Services/IPullRequestStatusBarManager.cs

@@ -4,6 +4,10 @@ namespace GitHub.InlineReviews.Services
 {
     public interface IPullRequestStatusBarManager
     {
+        /// <summary>
+        /// Place the PR status control on Visual Studio's status bar.
+        /// </summary>
+        /// <param name="mainWindow">The main window of Visual Studio.</param>
         void Initialize(Window mainWindow);
     }
 }

src/GitHub.InlineReviews/Services/PullRequestStatusBarManager.cs

@@ -42,6 +42,10 @@ public PullRequestStatusBarManager(IVSGitExt gitExt, Lazy<IPullRequestSessionMan
             this.serviceProvider = serviceProvider;
         }
 
+        /// <summary>
+        /// Lazily initialize when user enters the context of a GitHub repository.
+        /// </summary>
+        /// <param name="window">Visual Studio's main window.</param>
         public void Initialize(Window window)
         {
             mainWindow = window;