msaexp: NIRSpec analyis tools

What's Changed Fix bug in parsing MSA meta files with a list of source_ids by @gbrammer in https://github.com/gbrammer/msaexp/pull/35 Add option to split exposure groups by the act_id keyword by @gbrammer in https://github.com/gbrammer/msaexp/pull/37 Add functions for more robust template resampling by @gbrammer in https://github.com/gbrammer/msaexp/pull/36 Full Changelog: https://github.com/gbrammer/msaexp/compare/0.6.7...0.6.8Please cite this software using these metadata