v1.2.1 to fix `DutyCycle` and `New Period` display bugs

Releases v1.2.1

1. Fix DutyCycle bug. Check float precisison of DutyCycle only sometimes working #3
2. Fix New Period display bug. Check random dropouts #4
3. Update examples

v1.2.0 to add support to MegaCoreX core, fix `multiple-definitions` linker error, improve accuracy, optimize library code, etc.

Releases v1.2.0

1. Fix multiple-definitions linker error. Drop src_cpp and src_h directories
2. Add support to MegaCoreX core, including ATmega4809, ATmega4808, ATmega3209, ATmega3208, ATmega1609, ATmega1608, ATmega809 and ATmega808
3. Improve accuracy by using float, instead of uint32_t for dutycycle. Check Change Duty Cycle #1
4. DutyCycle to be optionally updated at the end current PWM period instead of immediately. Check DutyCycle to be updated at the end current PWM period #2
5. Optimize library code by using reference-passing instead of value-passing
6. Add example multiFileProject to demo for multiple-file project
7. Update examples accordingly

v1.1.0 to add functions to modify PWM settings on-the-fly

Releases v1.1.0

1. Add functions to modify PWM settings on-the-fly
2. Add example to demo how to modify PWM settings on-the-fly

v1.0.0 to support ISR-based multi-channel PWM for megaAVR-based boards ( UNO WiFi Rev2, AVR_Nano_Every, etc.), using megaAVR core

Initial Releases v1.0.0

1. Initial coding to support Arduino megaAVR boards, such as UNO WiFi Rev2, AVR_Nano_Every, etc., etc. using Arduino megaAVR core

2. The hybrid ISR-based PWM channels can generate from very low (much less than 1Hz) to highest PWM frequencies up to 500Hz with acceptable accuracy.