Build fails on Android Studio 3.4.x and 3.5, since libraries officially migrated to `androidx` #1

Thank you so much for publishing this wonderful guide with source code!

Would you be so kind as to do a quick update, please? There were significant changes in the Android development world since your post in January 2019.

For instance, as of May 2019, Google recommends Kotlin for new development of Android apps-- you were one step ahead! Migration to androidx is out of preview and official, such that becomes, etc. As noted in comments to the blog post, there are deprecation warnings when running the python-based utilities.

Would you also note library versions used, please?

The Rust parts seem fine as of rustc v1.37.0, as expected.

As I'm new to both Kotlin and Android development, it would be a while before I'd be able to submit a PR with any confidence for this issue-- sorry.