Update README.md

Author: hletrd

README.md

@@ -1,3 +1,8 @@
 # STM32ProMini
 - STM32 Pro Mini dev board
 - Based on STM32F411CEU6 MCU (100MHz ARM Cortex M4 CPU, 512kB Flash, 128kB SRAM)
+
+## Setup for Arduino IDE
+- Install STM32duino package along with STM32CubeProgrammer.
+- Add ```./variants/PROMINI_F411``` directory to Arduino IDE ```packages/STM32/hardware/stm32/(version)/variants``` directory.
+- Add the content of ```boards-add.txt``` to ```packages/STM32/hardware/stm32/(version)/boards.txt```.