Create brake pneumatics

We need pneumatics to activate the brakes. This means writing a subsystem and a command for the brakes that activates the piston.

In teleop, we want the brakes to be activated as long as a button is held—either a shoulder button or a trigger. Which one of these do we want to use?

- [x] Add subsystem
- [x] ~Add a control command~
- [x] Attach the command to the controls
- [ ] Test on the robot