Add samples kwarg and run docs example for 10000 samples

[Vaibhavdixit02]

Looks like the summation mismatch was only because of non-convergence.

Now with 50k samples

julia> sensres[:ρ_first_order] + sensres[:ρ_β_second_order], sensres[:ρ_total_order]
(0.9509424921787797, 0.9594158904145137)

julia> sensres[:β_first_order] + sensres[:ρ_β_second_order], sensres[:β_total_order]
(0.9136216916167716, 0.8971416879820884)