v1.6.0 to optimize code, etc.

### Releases v1.6.0

1. Add example [ISR_16_Timers_Array_OneShot](examples/ISR_16_Timers_Array_OneShot) to demo how to use `one-shot ISR-based timer`
2. Add example [multiFileProject](examples/multiFileProject) to demo for multiple-file project
3. Optimize code by using passing by `reference` instead of by `value`

Author: khoih-prog

README.md

@@ -59,6 +59,7 @@
   * [2. Change_Interval on ESP8266_NODEMCU_ESP12E](#2-change_interval-on-esp8266_nodemcu_esp12e)
   * [3. ISR_16_Timers_Array on ESP8266_NODEMCU_ESP12E](#3-isr_16_timers_array-on-esp8266_nodemcu_esp12e)
   * [4. ISR_16_Timers_Array_Complex on ESP8266_NODEMCU_ESP12E](#4-isr_16_timers_array_complex-on-esp8266_nodemcu_esp12e)
+  * [5. ISR_16_Timers_Array_OneShot on ESP8266_NODEMCU_ESP12E](#5-ISR_16_Timers_Array_OneShot-on-esp8266_nodemcu_esp12e)
 * [Debug](#debug)
 * [Troubleshooting](#troubleshooting)
 * [Issues](#issues)
@@ -180,7 +181,7 @@ The current library implementation, using `xyz-Impl.h` instead of standard `xyz.
 You can use
 
 ```
-#include "ESP8266TimerInterrupt.h"						 //https://github.com/khoih-prog/ESP8266TimerInterrupt
+#include "ESP8266TimerInterrupt.h"             //https://github.com/khoih-prog/ESP8266TimerInterrupt
 #include "ESP8266_ISR_Timer.hpp"               //https://github.com/khoih-prog/ESP8266TimerInterrupt
 ```