v1.2.0 to fix multiple-definitions linker error

### Major Releases v1.2.0

1. Fix `multiple-definitions` linker error.
2. Add example [multiFileProject](examples/multiFileProject) to demo for multiple-file project.

Author: khoih-prog

README.md

@@ -120,7 +120,7 @@ Currently, the library supports both new [**STM32 core v2.0.0+**](https://github
 
 ## Prerequisites
 
- 1. [`Arduino IDE 1.8.19+` for Arduino](https://www.arduino.cc/en/Main/Software)
+ 1. [`Arduino IDE 1.8.19+` for Arduino](https://github.com/arduino/Arduino). [![GitHub release](https://img.shields.io/github/release/arduino/Arduino.svg)](https://github.com/arduino/Arduino/releases/latest)
  2. [`Arduino Core for STM32 v2.2.0+`](https://github.com/stm32duino/Arduino_Core_STM32) for STM32 boards. [![GitHub release](https://img.shields.io/github/release/stm32duino/Arduino_Core_STM32.svg)](https://github.com/stm32duino/Arduino_Core_STM32/releases/latest)
 
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