Update issue template to describe what to do for different issue types

Closes spring-projectsgh-5519

.github/ISSUE_TEMPLATE.md

@@ -1,3 +1,20 @@
-<!-- 
-Thanks for raising a Spring Boot issue. Please provide a brief description of your problem along with the version of Spring Boot that you are using. If possible, please also consider putting together a sample application that reproduces the issue.
---> 
+<!--
+Thanks for raising a Spring Boot issue. What sort of issue are you raising?
+
+Question
+
+Please ask questions about how to use something, or to understand why something isn't
+working as you expect it to, on Stack Overflow using the spring-boot tag.
+
+Bug report
+
+Please provide details of the problem, including the version of Spring Boot that you
+are using. If possible, please provide a testcase or sample application that reproduces
+the problem. This makes it much easier for us to diagnose the problem and to verify that
+we have fixed it.
+
+Enhancement
+
+Please start by describing the problem that you are trying to solve. There may already
+be a solution, or there may be a way to solve it that you hadn't considered.
+-->