Reevaluate "onEditable"

I want to use the "code" or "tree" modes for viewing JSON in readonly mode. However, I want to be able to switch the editor into read/write mode dynamically. At the moment "onEditable" is not reevaluated - can I force JSONEditor to reevaluate whether the JSON can be edited? The only method I've found is to switch mode and then back again - but this comes with its own problems (like cursor location changing, tree collapsing).

```
const options = {
mode: 'code',
modes: ['code', 'form', 'text', 'tree', 'view', 'preview'],
onEditable: function () {
return self.editJSON; <-- this can change dynamically.
}
};
this.jsoneditor = new JSONEditor(container, options);
```

Perhaps something like?:

`this.jsoneditor.reevaluateOnEditable();`

Thanks,
-Neil