update issue template

.github/ISSUE_TEMPLATE.md

@@ -11,18 +11,22 @@ https://slate-slack.herokuapp.com/
 <!--
 For bugs, you **must** include the following:
 
-- A JSFiddle that minimally reproduces the issue.
 - A GIF showing the issue in action.
+- A sandbox that minimally reproduces the issue.
 - Information about your OS, browser, Slate version, etc.
 
 If you don't include these, there's a very good chance your issue will be closed, because it's much too hard to figure out exactly what is going wrong, and it makes maintenance much harder.
 
 We need to keep the issues actionable, or else maintaining Slate becomes overwhelming. Thank you for understanding!
 
-https://jsfiddle.net/fj9dvhom/1/
+https://codesandbox.io/s/slate-reproductions-k0tpx
 http://recordit.co/
 -->
 
+Slate: 0.XX.X
+Browser: Chrome / Safari / Firefox / Edge
+OS: Mac / Windows / Linux / iOS / Android
+
 #### What's the expected behavior?
 
 <!--
@@ -30,6 +34,8 @@ The fastest, and most appreciated way to have your issue fixed is to create a pu
 
 Slate is solving a pretty complex problem, and we can't do it without active contributors, so thank you so much for your help!
 
+https://docs.google.com/
+https://paper.dropbox.com/
 https://draftjs.org/
 http://prosemirror.net/
 https://quilljs.com/