v1.9.0 to add more Timers to SAMD21

### Releases v1.9.0

1. Add TC4, TC5, TCC1 and TCC2 Timers to SAMD21
2. Add example [SAMD21_MultiTimers](examples/SAMD21_MultiTimers) to demo the how to use all 6 SAMD21 timers simultaneously.
3. Add functions `attachInterruptInterval_MS()` and `setInterval_MS()`
4. Rewrite examples to take advantage of new functions and timers

Author: khoih-prog

README.md

@@ -67,12 +67,14 @@
   * [ 15. **SAMD21_MultiTimers**](examples/SAMD21_MultiTimers) **New**
 * [Example ISR_16_Timers_Array_Complex](#example-ISR_16_Timers_Array_Complex)
 * [Debug Terminal Output Samples](#debug-terminal-output-samples)
-  * [1. ISR_Timer_Complex_WiFiNINA on Arduino SAMD21 SAMD_NANO_33_IOT using WiFiNINA](#1-isr_timer_complex_wifinina-on-arduino-samd21-samd_nano_33_iot-using-wifinina)
-  * [2. TimerInterruptTest on Adafruit SAMD51 ITSYBITSY_M4](#2-timerinterrupttest-on-adafruit-samd51-itsybitsy_m4)
-  * [3. Argument_None on Arduino SAMD21 SAMD_NANO_33_IOT](#3-argument_none-on-arduino-samd21-samd_nano_33_iot)
-  * [4. ISR_16_Timers_Array on Arduino SAMD21 SAMD_NANO_33_IOT](#4-isr_16_timers_array-on-arduino-samd21-samd_nano_33_iot)
-  * [5. Change_Interval on Arduino SAMD21 SAMD_NANO_33_IOT](#5-change_interval-on-arduino-samd21-samd_nano_33_iot)
-  * [6. RepeatedAttachInterrupt_uS on SAMD21 SEEED_XIAO_M0](#6-repeatedattachinterrupt_us-on-samd21-seeed_xiao_m0)
+  * [1. ISR_Timer_Complex_WiFiNINA on Arduino SAMD21 SAMD_NANO_33_IOT using WiFiNINA](#1-ISR_Timer_Complex_WiFiNINA-on-Arduino-SAMD21-SAMD_NANO_33_IOT-using-WiFiNINA)
+  * [2. TimerInterruptTest on Adafruit SAMD51 ITSYBITSY_M4](#2-TimerInterruptTest-on-Adafruit-SAMD51-ITSYBITSY_M4)
+  * [3. Argument_None on Arduino SAMD21 SAMD_NANO_33_IOT](#3-Argument_None-on-Arduino-SAMD21-SAMD_NANO_33_IOT)
+  * [4. ISR_16_Timers_Array on Arduino SAMD21 SAMD_NANO_33_IOT](#4-ISR_16_Timers_Array-on-Arduino-SAMD21-SAMD_NANO_33_IOT)
+  * [5. Change_Interval on Arduino SAMD21 SAMD_NANO_33_IOT](#5-Change_Interval-on-Arduino-SAMD21-SAMD_NANO_33_IOT)
+  * [6. RepeatedAttachInterrupt_uS on SAMD21 SEEED_XIAO_M0](#6-RepeatedAttachInterrupt_uS-on-SAMD21-SEEED_XIAO_M0)
+  * [7. SAMD21_MultiTimers on SAMD21 SAMD_NANO_33_IOT](#7-SAMD21_MultiTimers-on-SAMD21-SAMD_NANO_33_IOT)
+  
 * [Debug](#debug)
 * [Troubleshooting](#troubleshooting)
 * [Issues](#issues)