v1.2.0 to optimize speed, add `PWM_SpeedTest`, etc

### Releases v1.2.0

1. Optimize speed with new `setPWM_DCPercentageInt_manual` function to improve speed almost 500 times compared to `setPWM`
2. Add example [PWM_manual](https://github.com/khoih-prog/SAMD_PWM/tree/main/examples/PWM_manual) to demo how to correctly use PWM to generate waveform. Check [About DCValue in setPWM_manual #2](khoih-prog/AVR_PWM#2)
3. Add example [PWM_SpeedTest](https://github.com/khoih-prog/SAMD_PWM/tree/main/examples/PWM_SpeedTest) to demo the better speed of new `setPWM_DCPercentageInt_manual` function
4. Breaking change: Modify `setPWM_manual` function to take `16-bit` dutycycle instead from merely `0-100` for better accuracy
5. Modify example [PWM_Waveform](https://github.com/khoih-prog/SAMD_PWM/tree/main/examples/PWM_Waveform) to adapt to breaking change of `setPWM_manual` function
6. Improve `README.md` so that links can be used in other sites, such as `PIO`
7. Bump up to v1.2.0 to sync with other Fast PWM libraries

v1.0.1 to add `PWM_StepperControl` example

### Releases v1.0.1

1. Add example [PWM_StepperControl](https://github.com/khoih-prog/SAMD_PWM/tree/main/examples/PWM_StepperControl) to demo how to control Stepper Motor using PWM

v1.0.0 for hardware-PWM on SAMD21/SAMD51 boards

### Releases v1.0.0

1. Initial coding for **SAMD21/SAMD51 boards** such as `NANO_33_IOT`, `ITSYBITSY_M4`, `SEEED_XIAO_M0`, `SparkFun SAMD51_Thing_Plus`, etc. using
- [Arduino SAMD core](https://github.com/arduino/ArduinoCore-samd)
- [Adafruit SAMD core](https://github.com/adafruit/ArduinoCore-samd)
- [Seeed-Studio SAMD core](https://github.com/Seeed-Studio/ArduinoCore-samd)
- [Sparkfun SAMD core](https://github.com/sparkfun/Arduino_Boards)
- [Industruino SAMD core](https://github.com/Industruino/IndustruinoSAMD)