fix: Scrollbar styling

closes #1665

app/components/Editor.js

@@ -92,6 +92,10 @@ const StyledEditor = styled(RichMarkdownEditor)`
     transition: ${(props) => props.theme.backgroundTransition};
   }
 
+  & * {
+    box-sizing: content-box;
+  }
+
   .notice-block.tip,
   .notice-block.warning {
     font-weight: 500;

shared/styles/theme.js

@@ -166,6 +166,9 @@ export const light = {
 
   noticeInfoBackground: colors.warmGrey,
   noticeInfoText: colors.almostBlack,
+
+  scrollbarBackground: colors.smoke,
+  scrollbarThumb: darken(0.15, colors.smokeDark),
 };
 
 export const dark = {
@@ -222,6 +225,9 @@ export const dark = {
 
   noticeInfoBackground: colors.white10,
   noticeInfoText: colors.almostWhite,
+
+  scrollbarBackground: colors.black,
+  scrollbarThumb: colors.lightBlack,
 };
 
 export default light;