* Create simple_schedule_plan.py

Many people have come on chat about creating schedules with the sdk and I just wanted to create a barebones example, so we can direct them to a public example.

* Update README.md

Updated readme to point at simple_schedule_plan example

* Update README.md

Update readme to link to new example of adding users to a group from a CSV.

* updated readme to point at script which updates prod branches touse main rather than master

Co-authored-by: Joel Dodge <joeldodge@google.com>
Co-authored-by: Dr. Strangelove <drstrangelove@google.com>