Update Serial documentation for additional boards

https://www.arduino.cc/reference/en/language/functions/communication/serial/

1) Document the NanoEvery Serial1 on pins 0 and 1 (tx, rx)

2) Document the Nano 33 BLE and BLE Sense Serial1 on pins tx and rx.
[https://docs.arduino.cc/hardware/nano-33-ble](url)
Document the possibility of an second hardware serial port per
[https://github.com/arduino/ArduinoCore-nRF528x-mbedos/issues/38](url)

```
UART mySerial(digitalPinToPinName(4), digitalPinToPinName(3), NC, NC);
//(change 4 and 3 as you prefer, the processor can mux any functionality on any pin)
//Note: the order of pins in the constructor is Tx, Rx, and is reversed from other Arduino serial/software serial constructors.
```

Start with the Arduino Serial reference page linked in the issue, then review the Nano Every and Nano 33 BLE hardware documentation and the referenced nRF528x-mbedos issue. Document Serial1 pins for both boards and the additional hardware serial option on the Nano 33 BLE and BLE Sense, including the UART constructor details shown in the issue.

Written by the indexing model from the issue text.