title: Angular Material: display matError with matTooltip
body: <p>I want to display the validation error with inside a bubble under the input, which is visible as long as the user focuses the element.
  Obviously this is not an easy task, and I gave up on my first try to do this only with CSS (cannot make it overly certain elements, what if the element is at the end of the page etc.).</p>
  
  <p>So I went back to the angular page and found the matTooltip, which behaves exactly as I want. (on top of other element, changes position when at the end of the page etc.) :) However I'm stuck on how to best combine those two.</p>
  
  <p>matError is tightly coupled with matFormField, matTooltip is more or less independent. </p>
  
  <p>Has somebody tried this or something similar?</p>