properly put escapes on strings

core/src/processing/data/IntDict.java

@@ -666,7 +666,7 @@ public class IntDict {
   public String toJSON() {
     StringList items = new StringList();
     for (int i = 0; i < size(); i++) {
-      items.append("\"" + keys[i] + "\": " + values[i]);
+      items.append("\"" + JSONObject.quote(keys[i]) + "\": " + values[i]);
     }
     return "{ " + items.join(", ") + " }";
   }

core/todo.txt

@@ -3,6 +3,7 @@ X some Table cleanup based on other CSV parsing work
 X use StandardCharsets.UTF_8 instead of getting encoding by name
 X PApplet.main(Blah.class) now works
 X add toJSON() method to IntDict
+X   had to use JSONObject.quote() to wrap the text
 _   do the same for the other data classes
 _   note the difference between this and toJSONObject() or toJSONArray()
 _   or is that the better way to handle it? hm