message: add Office 2019 support
diff: @@ -40,6 +40,8 @@ The following clients support Outlook add-ins.
  | Client | Supported API requirement sets |
  | --- | --- |
  +| Outlook 2019 for Windows | 1.1, 1.2, 1.3, 1.4, 1.5, 1.6 |
  +| Outlook 2019 for Mac | 1.1, 1.2, 1.3, 1.4, 1.5, 1.6 |
  | Outlook 2016 (Click-to-Run) for Windows | 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7 |
  | Outlook 2016 (MSI) for Windows | 1.1, 1.2, 1.3, 1.4 |
  | Outlook 2016 for Mac | 1.1, 1.2, 1.3, 1.4, 1.5, 1.6 |
  