How to increase the comment form up?

Question

css

There is a comment form (initially one line), the user writes some text.
By adding a new line, the shape is enlarged (which is correct) and the bottom edge goes down.
Because the comment form is located at the bottom of the window, the bottom of the form is hidden and you have to scroll the page to see the bottom of the comment.
Can you please tell me how to make the bottom of the form stay in place when adding a new line, and instead the top edge moves up, revealing the form?

Answer 1

As a result, I decided as follows:
I calculate the position of the bottom edge of the form, if it goes beyond the boundaries of the visible area, I do a scroll