Add compatibility layer for pims

[blakeNaccarato]

The flat metadata structure in boilercine facilitates serialization to file formats that expect flat metadata, such as NetCDF. The CINE reader implementation of pims may be a suitable substitute for the implementation in pycine, but the metadata layout in the pims implementation is nested, and has snake_case attributes rather than PascalCase coming from the original CINE file header. I think this is one situation where maintaining the source case convention is helpful, and only case-switching any properties that are surfaced out of the full set of metadata.

Add a from_* classmethod to Header that maps a pims CINE object to the existing Header dataclass, or something similar. Remember to add pims as a requirement and modify documentation to recommend that as the default CINE vendor.