Create ISSUE_TEMPLATE.md

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,3 @@
+Before writing your issue, check our instructions for [reporting bugs](https://github.com/caskroom/homebrew-cask#reporting-bugs) or [making requests](https://github.com/caskroom/homebrew-cask#requests), as appropriate. Those will walk you through the process.
+
+If none of those is appropriate, then **delete all this pre-inserted template text** and tell us your issue in as much detail as possible. Thank you for taking the time to correctly report the issue.