v1.2.1 to fix bug, etc.

### Releases v1.2.1

1. Fix `New Period` display bug. Check [random dropouts #4](khoih-prog/SAMD_Slow_PWM#4)
2. Display informational warning only when `_PWM_LOGLEVEL_` > 3
3. Update examples

Author: khoih-prog

CONTRIBUTING.md

@@ -15,7 +15,7 @@ If you don't find anything, please [open a new issue](https://github.com/khoih-p
 Please ensure to specify the following:
 
 * Arduino IDE version (e.g. 1.8.19) or Platform.io version
-* `RP2040` Core Version (e.g. Arduino-mbed RP2040 v2.6.1)
+* `RP2040` Core Version (e.g. Arduino-mbed RP2040 v2.7.2)
 * `RP2040` Board type (e.g. NANO_RP2040_CONNECT, RASPBERRY_PI_PICO, ADAFRUIT_FEATHER_RP2040, GENERIC_RP2040, etc.)
 * Contextual information (e.g. what you were trying to achieve)
 * Simplest possible steps to reproduce
@@ -28,10 +28,10 @@ Please ensure to specify the following:
 
 ```
 Arduino IDE version: 1.8.19
-Arduino-mbed mbed_nano v2.6.1
+Arduino-mbed mbed_nano v2.7.2
 NANO_RP2040_CONNECT Module
 OS: Ubuntu 20.04 LTS
-Linux xy-Inspiron-3593 5.4.0-96-generic #109-Ubuntu SMP Wed Jan 12 16:49:16 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 using TimerInterrupt.