Add revision code for 8GB model Raspberry Pi 4B

[SpasilliumNexus]

I have never tinkered with Python code before, so hopefully this submission is done correctly!

pi@Raspberry-Pi-4-Mini-PC:~ $ hostnamectl
   Static hostname: Raspberry-Pi-4-Mini-PC
         Icon name: computer
        Machine ID: 11581456297545d1956b016b5205d210
           Boot ID: e870aa05294a4bcba0518814f2bc2e6a
  Operating System: Debian GNU/Linux 10 (buster)
            Kernel: Linux 5.4.42-v8+
      Architecture: arm64

pi@Raspberry-Pi-4-Mini-PC:~ $ cat /proc/cpuinfo                                                                                                                                              
processor       : 0
BogoMIPS        : 108.00
Features        : fp asimd evtstrm crc32 cpuid
CPU implementer : 0x41
CPU architecture: 8
CPU variant     : 0x0
CPU part        : 0xd08
CPU revision    : 3

processor       : 1
BogoMIPS        : 108.00
Features        : fp asimd evtstrm crc32 cpuid
CPU implementer : 0x41
CPU architecture: 8
CPU variant     : 0x0
CPU part        : 0xd08
CPU revision    : 3

processor       : 2
BogoMIPS        : 108.00
Features        : fp asimd evtstrm crc32 cpuid
CPU implementer : 0x41
CPU architecture: 8
CPU variant     : 0x0
CPU part        : 0xd08
CPU revision    : 3

processor       : 3
BogoMIPS        : 108.00
Features        : fp asimd evtstrm crc32 cpuid
CPU implementer : 0x41
CPU architecture: 8
CPU variant     : 0x0
CPU part        : 0xd08
CPU revision    : 3

Hardware        : BCM2835
Revision        : d03114
Serial          : 10000000356fe6a3
Model           : Raspberry Pi 4 Model B Rev 1.4

pi@Raspberry-Pi-4-Mini-PC:~ $ python3 detect.py
Chip id:  BCM2XXX
Board id:  RASPBERRY_PI_4B

Is this a DragonBoard 410c? False
Is this a Pi 3B+? False
Is this a Pi 4B? True
Is this a 40-pin Raspberry Pi? True
Is this a Raspberry Pi Compute Module? False
Is this a BeagleBone Black? False
Is this a BeagleBone Green? False
Is this a Giant Board? False
Is this a Coral Edge TPU? False
Is this a SiFive Unleashed?  False
Is this a PYNQ Board? False
Is this a Rock Pi board? False
Is this a Clockwork Pi board? False
Is this an embedded Linux system? True
Is this a generic Linux PC? False
Is this a UDOO Bolt? False
Is this an OS environment variable special case? False
Raspberry Pi detected.

[ladyada]

rad, thanks :)