HardwareSerial has been tested on Uart0 (debug header) and Uart3 (i2c connector)
Software Serial has been tested to work bi-directionally at 9600 and 115200
using pins 6 and 63 on J5, and unidirectionally (write only) at 250000.
The code used to test was Teemuatlut's tmc2208 patch, and a few small changes to main used to echo recieved chars back to a host pc.

* Fix mistake in gitignore file and add in missing core files.

The missing leading slash on "lib" meant all folders names lib in the directory tree are ignored, rather than just the top level PlatformIO lib folder

* Add LiquidCrystal Library and associated headers modified to compile.

Fixes Arduino IDE builds for 8-bit AVR,
misc: Adafruit NeoPixel currently incompatible with Teensy 3.5-6, blacklisted