feat: allowing clearing of keystroke with ESC

I would have preferred to clear with right-click but the documentation
isn't forthcoming with how to override the right-click behavior on a
button. Hopefully no one wants to use ESC.

Also, added some boilerplate text when there is nothing bound.

Also, added the loading icon with "press any key" text while waiting for
input.

Author: ProgrammingByPermutation

src/Nullinside.TwitchStreamingTools/Controls/Keybind.axaml

@@ -3,10 +3,20 @@
              xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
              xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
              xmlns:viewModels="clr-namespace:Nullinside.TwitchStreamingTools.Controls.ViewModels"
+             xmlns:controls="clr-namespace:Nullinside.TwitchStreamingTools.Controls"
              mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
              x:Class="Nullinside.TwitchStreamingTools.Controls.Keybind"
              x:DataType="viewModels:KeybindViewModel">
     <StackPanel>
-        <Button Content="{Binding Keybind}" Command="{Binding ListenForKeystroke}" />
+        <Button IsVisible="{Binding !Listening}" 
+                Content="{Binding Keybind, TargetNullValue='[None]'}"
+                Command="{Binding ListenForKeystroke}" 
+                ToolTip.Tip="ESC to unset" />
+        <StackPanel IsVisible="{Binding Listening}"
+                    Orientation="Horizontal">
+            <controls:Loading Width="25" 
+                              Height="25" />
+            <Label>Press a key...</Label>
+        </StackPanel>
     </StackPanel>
 </UserControl>

src/Nullinside.TwitchStreamingTools/Controls/ViewModels/KeybindViewModel.cs

@@ -1,5 +1,6 @@
 using System.Reactive;
 
+using Nullinside.TwitchStreamingTools.Models;
 using Nullinside.TwitchStreamingTools.Services;
 using Nullinside.TwitchStreamingTools.ViewModels;
 
@@ -21,6 +22,11 @@ public class KeybindViewModel : ViewModelBase {
   /// </summary>
   private Keybind? _keybind;
 
+  /// <summary>
+  ///   True if listening for keystrokes, false otherwise.
+  /// </summary>
+  private bool _listening;
+
   /// <summary>
   ///   Initializes a new instance of the <see cref="KeybindViewModel" /> class.
   /// </summary>
@@ -38,6 +44,14 @@ public Keybind? Keybind {
     set => this.RaiseAndSetIfChanged(ref _keybind, value);
   }
 
+  /// <summary>
+  ///   True if listening for keystrokes, false otherwise.
+  /// </summary>
+  public bool Listening {
+    get => _listening;
+    set => this.RaiseAndSetIfChanged(ref _listening, value);
+  }
+
   /// <summary>
   ///   Listens for keystrokes.
   /// </summary>
@@ -47,6 +61,7 @@ public Keybind? Keybind {
   ///   Starts listening for keystrokes.
   /// </summary>
   private void StartListenKeystroke() {
+    Listening = true;
     _service.OnKeystroke -= OnKeystroke;
     _service.OnKeystroke += OnKeystroke;
   }
@@ -60,7 +75,8 @@ private void OnKeystroke(Keybind keybind) {
       return;
     }
 
-    Keybind = keybind;
+    Keybind = keybind.Key == Keys.Escape ? null : keybind;
     _service.OnKeystroke -= OnKeystroke;
+    Listening = false;
   }
 }