Provide build prerequisites

[GrahamJenkins]

The project README is incomplete. It describes cloning and building, but has no documentation about the prerequisites. I'm currently searching/testing/guessing my way through the errors.

Building specifically on Ubuntu 22.04, so far it appears that:

1. Java 8 is required (apt install openjdk-8-jre)

• If more versions are installed change defaults with sudo update-alternatives --config java

2. Android SDK is required and needs to be defined. I'm halfway through this, but apt install android-sdk seems to be correct, and the path needs to be found and added to the right environment variable or a local.properties (documentation or sample of this file required)
3. Is there a number 3? I'll update this once I figure out the second half of number 2.

[aaronisme]

Hi @GrahamJenkins Yes, you should use java8 for this repo. And We are on mac and using android studio. I think it can really helpful, you can directly use android studio which can be really helpful.