main/postmarketos-ui-asteroid: new aport

Building on the Mer packaging done for !2114 (merged), this packages the UI of AsteroidOS. Wait a smartwatch UI? We support just phones! Uh, nope. We support 2 smartwatches actually, we were just lacking a proper UI for them. Check device/testing/device-lg-dory and device/testing/device-lg-lenok.

So, this is Asteroid, a fully FOSS smartwatch UI building on the Mer stack that is also used by Glacier. It uses Qt5 and QML for the UI and apps. How well it works on our non-hybris using smartwatches is too be seen, but at least we have a reason to start supporting more smartwatches now!