network-block

Enables network blocking for specific classrooms:

1. Each block has its own file.
2. Blocks applies for 2h only when the file exists (naming as classroom-weekday-start).
3. This is the list of valid blocks:
   • ada-mon-19
   • ada-tue-19
   • ada-wed-16
   • torvalds-wed-19
   • torvalds-thu-19
   • torvalds-fri-16