* start uop docs
* only need show_labels
* sink comes first
* hotfix: invalid
* touchups
* 2 space indent works
* limit some buffer uops
* better BARRIER doc, Op -> UOp when it makes sense.
* make KernelInfo optional
* more work
relative links don't work
* this can be local in multi reduce+pads
* add UOps.SHAPETRACKER details
* UOps.CONST both types
* nit: local buffer isn't device Buffer, habit
* nit2: dtype -> DType
