Add issue template.

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,20 @@
+## Issue type
+Please specify the type of issue:
+- [ ] Specification
+- [ ] Code defect
+- [ ] Question
+
+## Steps to reproduce
+> What steps can reproduce the defect?
+> Please share the setup, sample project, target platform (desktop, core, uap)
+
+## Expected behavior
+> Share the expected output
+
+## Actual behavior
+> What is the behavior observed?
+
+## Environment
+> Please share additional details about the test environment.
+> Operating system, Build version of vstest.console, Package version of MSTest
+> framework and adapter