Battery Monitoring System - `bms`

# Summary

Add firmware to to monitor the status of the tractive system battery.

## Requirements

- [ ] Implement a BMS state machine which accepts commands
- [ ] Pulse a gpio pin every `100ms` to toggle an external WDT
- The pulse should only happen if all BMS checks are `OKAY`
- [ ] Disable WDT if the no BMS command is received from SPI
- [ ] Include CI unit tests

## Proposed Implementation

```bash
User/ADBMS6830.c/.h # Wrapper for SPI interface
User/BMS.c/h # BMS logic & state machine
Test/test_BMS.c/h # Unity tests
```

```c
BMS.h

// Fault codes
// Read cell voltages
// Read cell temperature

```

## Notes

- See datasheet for ADBMS6830 for SPI commands