Add an issue template for GitHub

Author: Holiverh

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,9 @@
+Please describe your issue in detail. Please also include any relevant
+stack traces or other error messages. Ideally, if possible, provide a
+small snippet that recreates the problem. Finally, fill in the applicable
+fields below which describe the environment you witnessed the issue in.
+
+- **Python-valve Version(s)**: ...
+- **Python Version(s)**: ...
+- **Operating System(s)/Platform(s)**: ...
+- **Game Server(s) and Version(s)**: ...