Ruggedize plyer_demo

[Julian-O]

This feature request boils down to "Let's do this right, or let's not do this."

This repository ostensibly contains a demo of plyer.

However:

• The demo itself is lacking, because plyer's strongest feature is that it works across a range of platforms. This demo only runs on one Android architecture. It needs to be improved to support all the plyer platforms, including the new Android architectures.

• The demo is lacking because it doesn't explain how to install it, including dependencies on Kivy and Plyer.

  • To that end, it is missing a setup.py.

• It is lacking a basic information about the project, including a readme, installation instructions, user guide, license, code of conduct, contributing guidelines.

• There is no sign it has been tested on the latest version of Plyer nor the latest version of Buildozer. There should be continuous integration scripts to show it does.

If this repo isn't worth the effort to make it a first-class product in the Kivy ecosystem, let's just delete it. It isn't necessary. Or migrate it into Plyer's test code base.