[closebrackets addon] Use editor line separator when exploding lines

Issue codemirror#5031

Author: Guan Gui

addon/edit/closebrackets.js

@@ -84,7 +84,8 @@
       if (!around || explode.indexOf(around) % 2 != 0) return CodeMirror.Pass;
     }
     cm.operation(function() {
-      cm.replaceSelection("\n\n", null);
+      var linesep = cm.lineSeparator() || "\n";
+      cm.replaceSelection(linesep + linesep, null);
       cm.execCommand("goCharLeft");
       ranges = cm.listSelections();
       for (var i = 0; i < ranges.length; i++) {