add an issue template

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,34 @@
+<!--
+Please follow the issue template below for bug reports and feature requests.
+Also please indicate in the issue title which language/library is concerned. Eg:  [JAVA] Bug generating foo with bar 
+-->
+
+##### Description
+
+<!-- describe what is the issue and why this is a problem for you. -->
+
+##### Swagger-codegen version
+
+<!-- which version of swagger-codegen are you using, is it a regression? -->
+
+##### Swagger declaration file content or url
+
+<!-- if it is a bug, a json or yaml that produces it. -->
+
+##### Command line used for generation
+
+<!-- including the language, libraries and various options -->
+
+##### Steps to reproduce
+
+<!-- unambiguous set of steps to reproduce the bug.-->
+
+##### Related issues
+
+<!-- has a similar issue been reported before? -->
+
+##### Suggest a Fix
+
+<!-- if you can't fix the bug yourself, perhaps you can point to what might be
+  causing the problem (line of code or commit) -->
+