v1.0.0 for nRF52 Slow PWM

### Initial Releases v1.0.0

1. Initial coding to support **nRF52-based boards, such as AdaFruit Itsy-Bitsy nRF52840, Feather nRF52840 Express**, etc. using [`Adafruit nRF52 core`](https://github.com/adafruit/Adafruit_nRF52_Arduino)

2. The hybrid ISR-based PWM channels can generate from very low (much less than 1Hz) to highest PWM frequencies up to 1000Hz with acceptable accuracy.

Author: khoih-prog

README.md

@@ -142,7 +142,7 @@ Another way to install is to:
 
 1. Install [VS Code](https://code.visualstudio.com/)
 2. Install [PlatformIO](https://platformio.org/platformio-ide)
-3. Install [**nRF52_Slow_PWM** library](https://platformio.org/lib/show/xxxxx/nRF52_Slow_PWM) by using [Library Manager](https://platformio.org/lib/show/xxxxx/nRF52_Slow_PWM/installation). Search for **nRF52_Slow_PWM** in [Platform.io Author's Libraries](https://platformio.org/lib/search?query=author:%22Khoi%20Hoang%22)
+3. Install [**nRF52_Slow_PWM** library](https://platformio.org/lib/show/12879/nRF52_Slow_PWM) by using [Library Manager](https://platformio.org/lib/show/12879/nRF52_Slow_PWM/installation). Search for **nRF52_Slow_PWM** 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)