Create SP2019 App Extension and update code to support SP2019 Modern View (Issues 144, 432, 433, 434, 435)

This is the initial release of the SharePoint 2019 App Extension to support Modern View. This update includes a new .sppkg file using the 2019 supported SharePoint Framework version, which is lower than the SharePoint Online version. It also includes updates to the tracking code to add tracking of SP2019 Modern View that is already included in our other tags.

Webtrends SharePoint 2019 Modern View Tag Installer v1.0.0.33
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