feat(data/rat/defs): add two lemmas for `pnat_denom` of 0 and 1 (#15864)
feat(data/rat/defs): add two lemmas for `pnat_denom` of 0 and 1 (#15864)




Co-authored-by: Jon Eugster <881fc59b2ec84f38153d9ae9c0b214e31ce61de4@gmail.com>

leanprover-community/mathlib,leanprover-community/mathlib