Implement an entry point module for roman_photoz

[stscijgbot-rstdms]

Issue RCAL-990 was created on JIRA by Mairan Teodoro:

We need to have a module that will serve as the entry point for new users of the roman_photoz package. Such entry point would setup the user's environment so that they can run {}roman_photoz{}. Once the entry point module is executed, it should create a catalog file containing synthetic data suitable for processing by {}roman_photoz{}.