Create issue_template.md

Author: fpistm

.github/issue_template.md

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+Please, before reporting any issue:
+- Make sure you are using the latest Arduino_Core_STM32 version.
+  https://github.com/stm32duino/Arduino_Core_STM32/releases/latest
+- Make sure the issue is not already reported or discussed on the [stm32duino forum](http://stm32duino.com)
+- Submit a GitHub issue only for reporting a problem related to the Arduino_Core_STM32.
+- **Avoid** to submit a GitHub issue for project troubleshooting.
+ 
+Any questions/feedback/sugestions should be discussed on the [stm32duino forum](http://stm32duino.com):
+  * questions on the [STM32 Core](http://stm32duino.com/viewforum.php?f=48)
+  * bugs/enhancements on the [STM core: Bugs and enhancements](http://stm32duino.com/viewforum.php?f=49)
+
+When reporting any issue, please try to provide all relevant information:
+
+- Complete source code which can be used to reproduce the issue. Please try to be as generic as possible (no extra code, extra hardware,...)
+- Which STM32 based board you used
+- If other hardware is required to reproduce the issue, please provide links or part numbers where this hardware can be purchased.
+- Which version of STM32 core and Arduino, Tools menu settings, operating system, ...
+
+Thanks