Add resample_signal to signals.tools module

[rafaelscsilva]

This PR adds the resample_signal function to the signals.tools module.

The function allows resampling of a signal from its original sampling rate to a new target sampling rate using scipy.signal.resample, by calculating required number of output samples with the original and new sampling frequencies. It supports both single- and multi-channel inputs.

Working Example

from biosppy import storage, signals

# load ecg signal from examples
ecg_signal, mdata = storage.load_txt('examples/ecg.txt')

# resample the signal to 500 Hz
resampled_ecg, = signals.tools.resample_signal(signal=ecg_signal,
                                               sampling_rate=mdata['sampling_rate'],
                                               resampling_rate=500)

[rafaelscsilva]

@sofia3ms I reverted the last commit, for the moment we can use the scipy's default behavior for resampling