feat(data/nat/factorial): non-strict inequality on factorial (#6052)
feat(data/nat/factorial): non-strict inequality on factorial (#6052)

Add lemmas add_factorial_le_factorial_add and  add_factorial_le_factorial_add'.  These are still used in the Liouville PR.

I should have added them to the previous PR on factorials, but they got lost on the way!





leanprover-community/mathlib,leanprover-community/mathlib