Merge pull request #3598 from alifeee/fix/r-stack-chrome

Fix `r-stack` overflow behaviour on Chromium browsers

css/layout.scss

@@ -25,6 +25,7 @@
 // Stack multiple elements on top of each other
 .reveal .r-stack {
 	display: grid;
+	grid-template-rows: 100%;
 }
 
 .reveal .r-stack > * {