Add option to clear the server cache (#487)

src/lib/graphql/mutations/ImageMutation.ts

@@ -0,0 +1,20 @@
+/*
+ * Copyright (C) Contributors to the Suwayomi project
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+import gql from 'graphql-tag';
+
+export const CLEAR_SERVER_CACHE = gql`
+    mutation CLEAR_SERVER_CACHE($input: ClearCachedImagesInput!) {
+        clearCachedImages(input: $input) {
+            clientMutationId
+            cachedPages
+            cachedThumbnails
+            downloadedThumbnails
+        }
+    }
+`;