use img in playlist card

+ use $black background on right sidebar

src/components/RightSideBar/Main.vue

@@ -1,6 +1,6 @@
 <template>
   <div
-    class="r-sidebar"
+    class="r-sidebar rounded"
     :style="{
       marginBottom: !settings.use_alt_np ? '-1rem' : '',
     }"
@@ -35,6 +35,7 @@ const settings = useSettingsStore();
 <style lang="scss">
 .r-sidebar {
   width: 100%;
+  background-color: $black;
 
   .grid {
     display: flex;