StickBackToTop now will animate like it used to do

package.json

@@ -96,6 +96,7 @@
     "secp256k1": "3.3.1",
     "semaphore": "^1.1.0",
     "semver": "^5.5.0",
+    "smoothscroll-polyfill": "^0.4.3",
     "source-map": "0.7.3",
     "source-map-support": "^0.5.4",
     "styled-components": "^3.3.2",

src/components/StickyBackToTop.js

@@ -5,6 +5,9 @@ import styled from 'styled-components'
 import Box from 'components/base/Box'
 import AngleUp from 'icons/AngleUp'
 import { GrowScrollContext } from './base/GrowScroll'
+import smoothscroll from 'smoothscroll-polyfill'
+
+smoothscroll.polyfill()
 
 const Container = styled(Box)`
   position: fixed;
@@ -75,7 +78,7 @@ class StickyBackToTop extends PureComponent<Props, State> {
     const { scrollContainer } = this.props.getGrowScroll()
     if (scrollContainer) {
       // $FlowFixMe seems to be missing in flow
-      scrollContainer.scrollTo(0, 0)
+      scrollContainer.scrollTo({ top: 0, behavior: 'smooth' })
     }
   }
 

yarn.lock

@@ -12808,6 +12808,10 @@ smart-buffer@^4.0.1:
   version "4.0.1"
   resolved "https://registry.yarnpkg.com/smart-buffer/-/smart-buffer-4.0.1.tgz#07ea1ca8d4db24eb4cac86537d7d18995221ace3"
 
+smoothscroll-polyfill@^0.4.3:
+  version "0.4.3"
+  resolved "https://registry.yarnpkg.com/smoothscroll-polyfill/-/smoothscroll-polyfill-0.4.3.tgz#94e5f2d604efcceb53f23ff0380d7ea7280d4bff"
+
 snapdragon-node@^2.0.1:
   version "2.1.1"
   resolved "https://registry.yarnpkg.com/snapdragon-node/-/snapdragon-node-2.1.1.tgz#6c175f86ff14bdb0724563e8f3c1b021a286853b"