fix: Spotify embed shows white background in dark mode

shared/editor/components/Frame.tsx

@@ -56,6 +56,7 @@ class Frame extends React.Component<PropsWithRef> {
       canonicalUrl,
       isSelected,
       referrerPolicy,
+      className = "",
       src,
     } = this.props;
     const withBar = !!(icon || canonicalUrl);
@@ -66,7 +67,9 @@ class Frame extends React.Component<PropsWithRef> {
         height={height}
         $withBar={withBar}
         $border={border}
-        className={isSelected ? "ProseMirror-selectednode" : ""}
+        className={
+          isSelected ? `ProseMirror-selectednode ${className}` : className
+        }
       >
         {this.isLoaded && (
           <Iframe