Add issue template to prevent dupes

.github/ISSUE_TEMPLATE.md

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+Please help prevent duplicate issues before submitting a new one:
+
+* [ ] I've searched other open/closed issues for duplicates before opening up this new issue.
+
+# Report
+
+## What did you do?
+
+ℹ Please replace this with what you did.  
+
+## What did you expect to happen?
+
+ℹ Please replace this with what you expected to happen.  
+
+## What happened instead?
+
+ℹ Please replace this with what happened instead (e.g. the issue).  
+
+