Add basic issue template

Author: michaelrevans

.github/issue_template.md

@@ -0,0 +1,9 @@
+**Do you want to request a *feature* or report a *bug*?**
+
+**What is the current behaviour?**
+
+**If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem. Your bug might get fixed faster if we can run your code and it doesn't have extra dependencies. Add a link to a sample repo and/or any relevant code below:**
+
+**What is the expected behaviour?**
+
+**Which versions of Matestack, and which browser/OS are affected by this issue? Did this work in previous versions of Matestack?**