Update placeholder data and make placeholder dir callbacks empty

src/App.css

@@ -63,6 +63,10 @@ body {
   background-color: #0056b3;
 }
 
+.PlaceholderItem {
+  animation: loading 1.5s infinite;
+}
+
 .PlaceholderItem > button,
 .ParentDirectoryItem > button {
 	background-color: #4D4F5D;
@@ -73,6 +77,15 @@ body {
 }
 
 .PlaceholderItem > button {
-  height: calc(16px + 10px * 2);
-  width: 6em;
+  height: calc(18px + 10px * 2);
+  min-width: 4em;
+}
+
+@keyframes loading {
+  0%, 100% {
+    filter: brightness(80%);
+  }
+  50% {
+    filter: brightness(100%);
+  }
 }

src/Gallery/index.tsx

@@ -68,7 +68,9 @@ function Contents(
       };
 
       if (item.is_dir) {
-        itemProps.onClick = () => {
+        itemProps.onClick = item.isPlaceholder
+          ? () => {}
+          : () => {
               const subCategory = getFileName(itemProps.url);
 
               if (category !== '') category = `${category}/${subCategory}`;
@@ -137,6 +139,14 @@ function getFileName(string: string): string {
 }
 
 function getPlaceholderData(): galleryItemInfo[] {
+  const backDir = (): galleryItemInfo => {
+    return {
+      is_dir: true,
+      url: '..',
+      thumbnail_url: '',
+      isPlaceholder: true,
+    };
+  };
   const placeholderDir = (): galleryItemInfo => {
     return {
       is_dir: true,
@@ -155,6 +165,7 @@ function getPlaceholderData(): galleryItemInfo[] {
   };
 
   return [
+    backDir(),
     placeholderDir(),
     placeholderDir(),
     placeholderImg(),