Initial v1.2.1 for Portenta_H7

### Initial Releases v1.2.1

1. Initial coding to support **Portenta_H7 boards** such as Portenta_H7 Rev2 ABX00042, etc., using [**ArduinoCore-mbed mbed_portenta** core](https://github.com/arduino/ArduinoCore-mbed)
2. Permit up to 16 super-long-time, super-accurate ISR-based timers to avoid being blocked
3. Using cpp code besides Impl.h code to use if Multiple-Definition linker error.
4. Bump version to v1.2.1 to sync with [STM32_TimerInterrupt library](https://github.com/khoih-prog/STM32_TimerInterrupt)

Author: khoih-prog

README.md

@@ -148,7 +148,7 @@ Another way to install is to:
 
 1. Install [VS Code](https://code.visualstudio.com/)
 2. Install [PlatformIO](https://platformio.org/platformio-ide)
-3. Install [**Portenta_H7_TimerInterrupt** library](https://platformio.org/lib/show/xxxxx/Portenta_H7_TimerInterrupt) or [**Portenta_H7_TimerInterrupt** library](https://platformio.org/lib/show/11419/Portenta_H7_TimerInterrupt) by using [Library Manager](https://platformio.org/lib/show/xxxxx/Portenta_H7_TimerInterrupt/installation). Search for **Portenta_H7_TimerInterrupt** in [Platform.io Author's Libraries](https://platformio.org/lib/search?query=author:%22Khoi%20Hoang%22)
+3. Install [**Portenta_H7_TimerInterrupt** library](https://platformio.org/lib/show/12828/Portenta_H7_TimerInterrupt) by using [Library Manager](https://platformio.org/lib/show/12828/Portenta_H7_TimerInterrupt/installation). Search for **Portenta_H7_TimerInterrupt** in [Platform.io Author's Libraries](https://platformio.org/lib/search?query=author:%22Khoi%20Hoang%22)
 4. Use included [platformio.ini](platformio/platformio.ini) file from examples to ensure that all dependent libraries will installed automatically. Please visit documentation for the other options and examples at [Project Configuration File](https://docs.platformio.org/page/projectconf.html)
 
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