added indicator for unavailable mediaitems

src/renderer/less/elements.less

@@ -965,6 +965,29 @@
     font-size: 12px;
   }
 
+  .unavailable-overlay {
+    position: absolute;
+    top: 0px;
+    left: 0px;
+    bottom: 0;
+    right: 0;
+    display: flex;
+    flex-direction: column;
+    align-items: center;
+    justify-content: center;
+    z-index: 2;
+    pointer-events: none;
+    background: rgb(0 0 0 / 40%);
+    margin: 2em;
+    border-radius: 10px;
+
+    >.codicon {
+      font-size: 4em;
+      font-weight: bold;
+      opacity: 0.5;
+    }
+  }
+
   &.mediaitem-video {
     height: 200px;
     width: 240px;