Mechanical drawings for touchpad module

[cscott]

Thank you so much for the touchpad electrical specs requested in issue #8!

Just for tracking purposes, I'm opening this task for the mechanical information about the touchpad module, which is all that is now missing to be able to make a "blank spacer" type touchpad module, or to make a "double-height" keyboard module. This sort of overlaps with issue #7, in that with drawings for the midplate one could probably figure this out, but it would be nice to have drawings of the touchpad module with the same level of detail as were given for the small and medium input modules.