v1.0.0 for AVR Slow PWM

### Initial Releases v1.0.0

1. Initial coding to support **AVR boards, such as Mega-2560, UNO,Nano, Leonardo, etc.**, etc. using AVR core

2. The hybrid ISR-based PWM channels can generate from very low (much less than 1Hz) to highest PWM frequencies up to 500Hz with acceptable accuracy.

Author: khoih-prog

CONTRIBUTING.md

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+## Contributing to nRF52_Slow_PWM
+
+### Reporting Bugs
+
+Please report bugs in nRF52_Slow_PWM if you find them.
+
+However, before reporting a bug please check through the following:
+
+* [Existing Open Issues](https://github.com/khoih-prog/nRF52_Slow_PWM/issues) - someone might have already encountered this.
+
+If you don't find anything, please [open a new issue](https://github.com/khoih-prog/nRF52_Slow_PWM/issues/new).
+
+### How to submit a bug report
+
+Please ensure to specify the following:
+
+* Arduino IDE version (e.g. 1.8.16) or Platform.io version
+* `nRF52` Core Version (e.g. Adafruit nRF52 core v1.0.0)
+* 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: 1.8.16
+Arduino NRF52 Core Version 1.0.0
+OS: Ubuntu 20.04 LTS
+Linux xy-Inspiron-3593 5.4.0-80-generic #90-Ubuntu SMP Fri Jul 9 22:49:44 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
+
+Context:
+I encountered a crash while trying to use the Timer Interrupt.
+
+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/nRF52_Slow_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!

LICENSE

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+MIT License
+
+Copyright (c) 2019 Khoi Hoang
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.