Fixes the modal animating off screen

While using `position: absolute` the modal window will animate relative
to the top of the viewport, i.e., it will always appear where the bottom
of the viewport is when `document.body.scrollTop === 0`. By setting
`position: fixed`, the modal positions itself to the viewport and
therefore will always be visible

components/Modal/ModalAnimator.css

@@ -3,7 +3,7 @@
 }
 
 .root {
-  position: absolute;
+  position: fixed;
   height: 100%;
   width: 100%;
   top: 0;
@@ -17,7 +17,7 @@
 }
 
 .overlay {
-  position: absolute;
+  position: fixed;
   width: 100%;
   height: 100%;
   background-color: var(--overlay-default);
@@ -31,15 +31,15 @@
 }
 
 .wrapper {
-  position: absolute;
+  position: fixed;
   height: 100%;
   width: 100%;
   will-change: transform;
   backface-visibility: hidden;
 }
 
 .window {
-  position: absolute;
+  position: fixed;
   left: 50%;
   bottom: 0;
   width: 100%;