v1.0.0 for hardware-PWM on Teensy boards

### Initial Releases v1.0.0

1. Initial coding to support **Teensy 4.x boards, such as Teensy 4.0, Teensy 4.1, Teensy MicroMod, etc.**, using [Teensyduno core](https://www.pjrc.com/teensy/td_download.html). The support to **Teensy 2.x, Teensy LC and Teensy 3.x** will be added gradually.

CONTRIBUTING.md

@@ -0,0 +1,71 @@
+## Contributing to Teensy_PWM
+
+### Reporting Bugs
+
+Please report bugs in Teensy_PWM if you find them.
+
+However, before reporting a bug please check through the following:
+
+* [Existing Open Issues](https://github.com/khoih-prog/Teensy_PWM/issues) - someone might have already encountered this.
+
+If you don't find anything, please [open a new issue](https://github.com/khoih-prog/Teensy_PWM/issues/new).
+
+### How to submit a bug report
+
+Please ensure to specify the following:
+
+* Arduino IDE version (e.g. 1.8.19) or Platform.io version
+* `Teensyduino` Core Version (e.g. Teensy core v1.57)
+* Contextual information (e.g. what you were trying to achieve)
+* Simplest possible steps to reproduce
+* Anything that might be relevant in your opinion, such as:
+  * Operating system (Windows, Ubuntu, etc.) and the output of `uname -a`
+  * Network configuration
+
+
+### Example
+
+```
+Arduino IDE version: 1.8.19
+Teensyduino Core Version 1.57
+OS: Ubuntu 20.04 LTS
+Linux xy-Inspiron-3593 5.15.0-52-generic #58~20.04.1-Ubuntu SMP Thu Oct 13 13:09:46 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
+
+Context:
+I encountered a crash while using this library
+
+Steps to reproduce:
+1. ...
+2. ...
+3. ...
+4. ...
+```
+
+---
+
+### Sending Feature Requests
+
+Feel free to post feature requests. It's helpful if you can explain exactly why the feature would be useful.
+
+There are usually some outstanding feature requests in the [existing issues list](https://github.com/khoih-prog/Teensy_PWM/issues?q=is%3Aopen+is%3Aissue+label%3Aenhancement), feel free to add comments to them.
+
+---
+
+### Sending Pull Requests
+
+Pull Requests with changes and fixes are also welcome!
+
+Please use the `astyle` to reformat the updated library code as follows (demo for Ubuntu Linux)
+
+1. Change directory to the library GitHub
+
+```
+xy@xy-Inspiron-3593:~$ cd Arduino/xy/Teensy_PWM_GitHub/
+xy@xy-Inspiron-3593:~/Arduino/xy/Teensy_PWM_GitHub$
+```
+
+2. Issue astyle command
+
+```
+xy@xy-Inspiron-3593:~/Arduino/xy/Teensy_PWM_GitHub$ bash utils/restyle.sh
+```