Adds noise to mass domain
add_noise(replicate_curve, standard_deviations)`data.table` with technical replicates of a
deuteration curve (one element of a list obtained by
get_deuteration_curves_from_spectra)
named vector of standard deviations
`data.table` containing a single noisy curve (for one replication).
The noise is sampled from normal distribution with mean 0
and standard deviation equal to per_run_deviations and added to the
Mass values unless they are not zeroes (there is no noise at the time
0).