escaping \n and \r

I thought I could do it before passing the value to the generator but sadly that is not so easy xD

```ruby
require 'ox'

str = "line1\nline2"

str.gsub!("\n", '&#10;')

node = Ox::Element.new('name')
node << str

p Ox.dump(node)
=> "\n<name>line1&amp;#10;line2</name>\n"
```

I need to keep the xml on one line so I was looking for a way to escape these two to &#10; and &#13; respectively but I can't figure out a way to do so without modifying the gem's code (and even there honestly I am not sure where to look)