Improve scrolling behavior

Prevent scrolling in the sidebar/ content area scrolling the other section when the boundary of a scrolling area is reached.

https://developer.mozilla.org/en-US/docs/Web/CSS/overscroll-behavior

app/components/Scrollable/Scrollable.js

@@ -5,6 +5,7 @@ const Scrollable = styled.div`
   height: 100%;
   overflow-y: auto;
   overflow-x: hidden;
+  overscroll-behavior: none;
   -webkit-overflow-scrolling: touch;
 `;