Create script to auto update `calendar_dates.txt`

[albertkun]

• [ ] ~Set up automation that takes the new calendar_dates.txt and replaces it within the current GTFS zip file, generating a new updated GTFS zip file.~
• [ ] ~Set up automation that commits that new GTFS zip file to the repository and pushes it to GitLab.~
• [x] Set up automation that takes the new calendar_dates.txt, commits it to the repository and pushes it to GitLab.
• [x] Set up automation that removes uses the data in the new calendar_dates.txt to replace the two-week span in the original calendar_dates.txt, commits that to the repository and pushes it to GitLab.
• [x] Confirm with Rollin Baker that the logic is sound and our path forward is aligned.
• [ ] ~#11~

[matikin9]

@albertkun - Working notebook pushed to the jupyter-notebook branch in GitLab: https://gitlab.com/LACMTA/gtfs_bus/-/tree/jupyter-notebook