title: Change animation to always open mat expansion panel vertically downwards
body: <p>I have tried looking into the angular/material and angular/animation files to understand what I need to change in order to have the expansion panel open animation to only open downwards. This could be based on the positioning of the panel header tab in the html page such that if it is below the center line, it opens upwards and if the tab is above it, then panel opens downwards. I haven't been able to find the variable that controls this, whether in a css or ts file, so your help is much appreciated to figure out how to do this!</p>