Update findGalleries to only fetch imageCount instead of all images (#941)

graphql/documents/data/gallery-slim.graphql

@@ -0,0 +1,28 @@
+fragment GallerySlimData on Gallery {
+  id
+  checksum
+  path
+  title
+  date
+  url
+  details
+  rating
+  image_count
+  cover {
+    ...SlimImageData
+  }
+  studio {
+    ...StudioData
+  }
+  tags {
+    ...TagData
+  }
+  performers {
+    ...PerformerData
+  }
+  scene {
+    id
+    title
+    path
+  }
+}

graphql/documents/queries/gallery.graphql

@@ -2,7 +2,7 @@ query FindGalleries($filter: FindFilterType, $gallery_filter: GalleryFilterType)
   findGalleries(gallery_filter: $gallery_filter, filter: $filter) {
     count
     galleries {
-      ...GalleryData
+      ...GallerySlimData
     }
   }
 }
@@ -11,4 +11,4 @@ query FindGallery($id: ID!) {
   findGallery(id: $id) {
     ...GalleryData
   }
-}
+}