Renamed a playground variable to avoid a S/FF bug

ISSUE_TEMPLATE.md

@@ -3,7 +3,7 @@ Thanks for using react-virtualized! :)
 Before creating an issue...
 
 # Are you asking a question?
-Please don't file Github issues to ask questions. Use Stack Overflow with a #react-virtualized tag [http://stackoverflow.com/questions/tagged/react-virtualized] or ask in the react-virtualized Slack channel [https://react-virtualized.now.sh].
+Please don't file GitHub issues to ask questions. Use Stack Overflow with a #react-virtualized tag [http://stackoverflow.com/questions/tagged/react-virtualized] or ask in the react-virtualized Slack channel [https://react-virtualized.now.sh].
 
 # Are you reporting a bug or runtime error?
 Please include either a failing unit test or a Plnkr demonstrating the bug you are reporting. You can start by forking this Plnk! https://plnkr.co/edit/6syKo8cx3RfoO96hXFT1
@@ -14,4 +14,4 @@ You may also find the online Babel tool (https://babeljs.io/repl/) quite helpful
 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 me 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.)
+* Can you point to similar functionality with any existing libraries or components? (Working demos can be helpful.)

playground/chat.js

@@ -278,17 +278,17 @@ for (var i = 0; i < 1000; i++) {
   })
 }
 
-const mount = document.querySelector('#mount')
+const container = document.getElementById('mount')
 
 ReactDOM.render(
   React.createElement(App),
-  mount
+  container
 )
 
 document.body.addEventListener('click', function () {
   const bodyWidth = document.body.getBoundingClientRect().width
   const minWidth = 300
 
-  mount.style.display = 'inline-block'
-  mount.style.maxWidth = `${minWidth + Math.round(Math.random() * (bodyWidth - minWidth))}px`
+  container.style.display = 'inline-block'
+  container.style.maxWidth = `${minWidth + Math.round(Math.random() * (bodyWidth - minWidth))}px`
 })