Add Teensy 4 boards to supported boards doc

[skip ci]

Author: dmadison

extras/SupportedBoards.md

@@ -26,9 +26,12 @@ Here is a complete list of all of the currently supported boards. Each header li
 * [Qduino Mini](https://www.sparkfun.com/products/13614)
 * [LilyPad USB Plus](https://www.sparkfun.com/products/14346)
 
-## [Teensy 3 Boards](https://github.com/dmadison/ArduinoXInput_Teensy/)
+## [Teensy Boards](https://github.com/dmadison/ArduinoXInput_Teensy/)
 
 * [Teensy 3.6](https://www.pjrc.com/store/teensy36.html)
 * [Teensy 3.5](https://www.pjrc.com/store/teensy35.html)
 * [Teensy 3.1](https://www.pjrc.com/store/teensy31.html) / [3.2](https://www.pjrc.com/store/teensy32.html)
-* [Teensy LC](https://www.pjrc.com/teensy/teensyLC.html)
+* [Teensy LC](https://www.pjrc.com/store/teensylc.html)
+* [Teensy 4.0](https://www.pjrc.com/store/teensy40.html)
+* [Teensy 4.1](https://www.pjrc.com/store/teensy41.html)
+* [Teensy MicroMod](https://www.sparkfun.com/products/16402)