README: Tidy readme and fix warnings
Tidy README and fix warnings.
/home/jakob/XR/xr-runtime/README.md:68: warning: unable to resolve reference to `https:' for \ref command
/home/jakob/XR/xr-runtime/README.md:68: warning: unable to resolve reference to `https:' for \ref command
``
Edited by Jakob Bornecrantz