feat: add estimatePrecursorMz function (issue #315)

[jorainer]

• Add the estimatePrecursorMz functions to estimate/adjust the reported precursor m/z for DDA spectra.

This PR fixes issue #315 , i.e. for DDA data from Waters instruments, the reported precursor m/z value might not be correct because it is not being corrected through the lockmass calibration. Would also be good to get hold of some more (different) Waters DDA files to check.

[philouail]

All good to me, super cool function and good that this issue was discovered ! I was just confused by one paragraph in the documentation, I put an alternative in case.

[jorainer]

@mar-garcia , can you please check the documentation of the function? just to ensure it's correct and describes the problem properly.

[mar-garcia]

Not sure how I can check the documentation.... I've just checked what is written here: https://github.com/rformassspectrometry/Spectra/blob/adjust_precursor_mz/R/Spectra-estimatePrecursorMz.R
The only small detail I would add the specifcation "in the previous MS1 spectrum" in the following sentence:
Thus, for each fragment spectrum, this method identifies in the previous MS1 spectrum the peak with the highest intensity and an m/z value similar to the fragment spectrum's reported precursor m/z (given parameters tolerance and ppm).

[jorainer]

that's perfect, thanks @mar-garcia !