feat(iText): Add optional hiddenTextareaContainer to contain hiddenTextarea

[rockerBOO]

This is to prevent laggy conditions where the entire body needs to be redrawn. We can attach somewhere else off of the main body tag.

Some details into the scenario but this is a little different due to not making a lot of new elements. But in large pages it can cause additional lag to attach.

const textbox = new Textbox('yo', { hiddenTextareaAppendTo: document.getElementById('hiddenTextarea') })

Not 100% into the long variable name but felt appropriate.

[asturur]

I like this, is ok, it solves also issues with people using this inside a modal that block any kind of text events from going outside of it