Add parallelization for large pointing sequences

[0.6.4] - 2022-07-04

New

• ZodiPy can now compute the emission in parallel by distributing the pointing over multiple processes. This is useful for large pointing sequences or making binned maps with large nside where the execution would be slow due to the massive amount of line of sights that needs to be evaluated. This feature is disabled by default, but is activated by initializing Zodipy with parallel=True. Optionally, the user may also specify the number of desired processes with the n_proc argument. See the new Parallel computations section in the documentation for an example of how to use ZodiPy with this feature.