message: doc: add UWP docs link to AddASetting.md
  Since we're following the UWP design guidance, we should recommend the community use it as well when adding new settings to the settings UI.
diff: @@ -336,6 +336,8 @@ INITIALIZE_BINDABLE_ENUM_SETTING(LaunchMode, LaunchMode, LaunchMode, L"Globals_L
  ### Updating the UI
  +When adding a setting to the UI, make sure you follow the [UWP design guidance](https://docs.microsoft.com/windows/uwp/design/).
  +
  #### Enum Settings
  Now, create a XAML control in the relevant XAML file. Use the following tips and tricks to style everything appropriately:
  