Add missing SEC college football cities (Oxford MS, Starkville MS, College Station TX)

The city-timezones library is missing three SEC college football cities that are needed for accurate timezone lookups:
- Oxford, Mississippi (Ole Miss)
- Starkville, Mississippi (Mississippi State)  
- College Station, Texas (Texas A&M)

All three cities are in the Central Time Zone (America/Chicago). Adding these cities will improve the library's coverage for college sports applications.