Add README.md

[ruzko]

I'm trying to pass location data from host system running geoclue-2 (d-bus) to waydroid, and came across this project.

It would be neat if this project had a short readme explaining what sensors are supported, usecases, and maybe a guide :)

Figuring out whether this project does or could cover mine and others' usecases is possible by reading the source code, but the bar to implement and contribute will be lowered a lot by having a README