chore(github): add issue template

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,27 @@
+### Thanks for using nivo
+
+Before creating an issue...
+
+# Are you asking a question?
+
+Please don't file GitHub issues to ask questions.
+Try to use the discord channel first: https://discord.gg/n7Ft74f.
+
+
+# Are you reporting a bug/error?
+
+Please include a test case that demonstrates the issue you're reporting.
+This is very critical to maintainers in order to help us see the issue you're seeing.
+
+I already have several existing examples on codesandbox, you can fork one of them
+depending on the component you're working on: https://codesandbox.io/u/plouc/sandboxes
+
+
+# Are you making a feature request?
+
+Provide as much information as possible about your requested feature.
+Here are a few questions you may consider answering:
+
+*   What's your use case? (Tell us about your application and what problem you're trying to solve.)
+*   What interface do you have in mind? (What new properties or methods do you think might be helpful?)
+*   Can you point to similar functionality with any existing libraries or components? (Working demos can be helpful.)