Merge pull request #6093 from matrix-org/jryans/firefox-overscroll

Stop overscroll in Firefox Nightly for macOS

res/css/_common.scss

@@ -45,6 +45,8 @@ html {
        N.B. Breaks things when we have legitimate horizontal overscroll */
     height: 100%;
     overflow: hidden;
+    // Stop similar overscroll bounce in Firefox Nightly for macOS
+    overscroll-behavior: none;
 }
 
 body {