Include MAX31865 library (#15969)

platformio.ini

@@ -29,6 +29,7 @@ lib_deps =
   LiquidCrystal@1.3.4
   TMCStepper@>=0.5.2,<1.0.0
   Adafruit NeoPixel@1.2.5
+  Adafruit_MAX31865=https://github.com/adafruit/Adafruit_MAX31865/archive/master.zip
   LiquidTWI2=https://github.com/lincomatic/LiquidTWI2/archive/master.zip
   Arduino-L6470=https://github.com/ameyer/Arduino-L6470/archive/dev.zip
   SailfishLCD=https://github.com/mikeshub/SailfishLCD/archive/master.zip