chore(playground): add ruler for inputEditor (#3221)

website/static/playground.js

@@ -291,6 +291,10 @@ function setEditorStyles() {
   outputEditor.setOption("mode", mode);
   output2Editor.setOption("mode", mode);
 
+  inputEditor.setOption("rulers", [
+    { column: options.printWidth, color: "#eeeeee" }
+  ]);
+
   [outputEditor, output2Editor].forEach(function(editor) {
     editor.setOption("rulers", [
       { column: options.printWidth, color: "#444444" }