Integrate MALDIquant's baseline estimation #119

[lgatto]

Addresses #119

[lgatto]

The GHA fails - I have tried to fiddle with it, so just ignore the workflow file for now. (Or any advise welcome)

[lgatto]

General points to consider for this review:

1. Example data used in ?estimateBaseline comes from MALDIquant, which is thus now in suggest, rather than part of the package itself (size is about 0.5 Mb)
2. There's one single estimateBaseline() function with a method argument. We could also provide individual estimateBaselineSNIP(), estimateBaselineTopHat(), esimateBaselineConvexHull() and estimateBaselineMedian().

[lgatto]

In addition to using simulated example data, I also export the individual estimateBaseline[Snip|TopHat|ConvexHub|Media]() functions. I think this makes arguments explicit, and clarifies the manual page. The main estimateBaseline() function is still available, so as to remain backward compatible with the signature in MALDIquant.

[sgibb]

Thanks @lgatto for integrating the baseline estimation algorithms!

I just changed some values for the iteration/half window sizes to demonstrate the difference in the simulated data.

[lgatto]

Thank you @sgibb!