Got oneline textareas to show

The issue is that one line textareas are impossible with the current methods, because of browser functionality of `height: auto`.
A textarea's with height style set to auto will always have a scrollheight greater or equal to two lines.
Therefore, setting height to auto and then setting height to scroll height will never result in one line, even if the content only takes up one line.

My solution is to add an invisible div, that visually replicates the textarea, and get the height from there.

I still need to test and make sure div and textarea match up in all prop/style cases.