command line support for windows
@rhys.poulton reports that the command line utility does not work on windows:
(base) C:\Users\poulton>gpstime
'gpstime' is not recognized as an internal or external command,
operable program or batch file.
The CLI is currently distributed as a shell script so as to avoid the overhead of it being generated as an entry point. However, we would probably get windows support if it was an entry_point.