Added GitHub issue template

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,11 @@
+<!--
+Thanks for using ArduinoJson :-)
+
+Before opening an issue, please make sure you've read these:
+https://github.com/bblanchon/ArduinoJson/wiki/FAQ
+https://github.com/bblanchon/ArduinoJson/wiki/Avoiding-pitfalls
+
+Next, make sure you provide all the relevant information: platform, code snippet, and error messages.
+
+Please be concise!
+-->