v1.2.1 to fix DutyCycle bug, etc.

### Releases v1.2.1

1. Fix `DutyCycle` bug. Check [float precisison of DutyCycle only sometimes working #3](khoih-prog/SAMD_Slow_PWM#3)
2. Fix `New Period` display bug. Check [random dropouts #4](khoih-prog/SAMD_Slow_PWM#4)
3. Update examples

Author: khoih-prog

CONTRIBUTING.md

@@ -29,7 +29,7 @@ Please ensure to specify the following:
 Arduino IDE version: 1.8.19
 Teensyduino Core Version 1.56
 OS: Ubuntu 20.04 LTS
-Linux xy-Inspiron-3593 5.4.0-99-generic #112-Ubuntu SMP Thu Feb 3 13:50:55 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
+Linux xy-Inspiron-3593 5.4.0-100-generic #113-Ubuntu SMP Thu Feb 3 18:43:29 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
 
 Context:
 I encountered a crash while trying to use the Timer Interrupt.