Shift fix and cursor offset

[levexis]

These changes allow for an offset to provide a workaround for issue 28 raycaster collision tracking at small scales. That issue requires more investigation as there is still some drift but this at least improves things.

When testing I noticed the shift key no longer works so I have implemented a quick fix. I might take a look at adding support for using both hands which will require another key plane and a little refactoring as per issue 17

I presume you want the build script run on pull releases, if not let me know.

Paul

[levexis]

also, as you will see, I added an example that shows using the keyboard on a touch controller (called wrist).