Make shortform demo work on Android TV

[gramound]

The short form content demo is missing the leanback launcher intent filter and its viewpager2 is unable to scroll with d-pad key events (have to inject swipe events from adb).

I will submit a pull request.

[marcbaechinger]

Thanks for the report and the PR. I have taken this into review.

The app is obviously not ready for TV as you noticed. Support for D-Pad that you added is a first step.
The layout is still questionable on TV because the surface is simply filling the entire screen which distorts the media.

I'll process your PR and then as an internal follow-up we have to give the UI some love so it works better on any device and layout.