Added a sub2 level

[fxpar]

Hi,
Just needed to add another row of text below to have degree and notes (random values here). I added a sub2 version for the attribute and the parse function, and added it to the render function. Works fine 👍

Thanks a lot.

Cheers

[fxpar]

Demo at: https://fxpar.github.io/uke-chord/
With ugly code... sorry, not good enough to make a pull request.