Move core files into new folder

src/Base.types.ts

@@ -0,0 +1,18 @@
+/*
+ * 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 { ParseKeys } from 'i18next';
+
+export enum DirectionOffset {
+    PREVIOUS = -1,
+    NEXT = 1,
+}
+
+export type NullAndUndefined<T> = T | null | undefined;
+
+export type TranslationKey = ParseKeys;