v1.7.1 for Teensy41 and QNEthernet

### Releases v1.7.1

1. Initial porting and coding for **Teensy 4.1 using built-in QNEthernet**
2. Bump up version to v1.7.1 to sync with [AsyncHTTPRequest_Generic](https://github.com/khoih-prog/AsyncHTTPRequest_Generic) v1.7.1

Author: khoih-prog

CONTRIBUTING.md

@@ -0,0 +1,55 @@
+## Contributing to AsyncWebServer_Teensy41
+
+### Reporting Bugs
+
+Please report bugs in AsyncWebServer_Teensy41 if you find them.
+
+However, before reporting a bug please check through the following:
+
+* [Existing Open Issues](https://github.com/khoih-prog/AsyncWebServer_Teensy41/issues) - someone might have already encountered this.
+
+If you don't find anything, please [open a new issue](https://github.com/khoih-prog/AsyncWebServer_Teensy41/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. `Teensyduino core v1.56`)
+* `QNEthernet` library version (e.g. `QNEthernet v0.13.0`)
+* Board type and relevant info
+* 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 v1.56
+Teensy 4.1 using QNEthernet v0.13.0
+OS: Ubuntu 20.04 LTS
+Linux xy-Inspiron-3593 5.13.0-35-generic #40~20.04.1-Ubuntu SMP Mon Mar 7 09:18:32 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
+
+Context:
+I encountered an endless loop while trying to connect to Local WiFi.
+
+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/AsyncWebServer_Teensy41/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!
+