add translation keys (#246)

* Fix i18n tsc issue

"t" can return null by default.
This was already disabled in the config, but it had no effect on tsc.

* Fix translation in "DefaultNavBar"

key was missing and since this is a constant the translation wouldn't update in case the language got changed after first load.

* Enable typing for i18n translation keys

* Add translation keys

src/screens/settings/DefaultReaderSettings.tsx

@@ -21,11 +21,13 @@ import {
 } from 'util/readerSettings';
 import ReaderSettingsOptions from 'components/reader/ReaderSettingsOptions';
 import { IReaderSettings } from 'typings';
+import { useTranslation } from 'react-i18next';
 
 export default function DefaultReaderSettings() {
+    const { t } = useTranslation();
     const { setTitle, setAction } = useContext(NavbarContext);
     useEffect(() => {
-        setTitle('Default Reader Settings');
+        setTitle(t('reader.settings.title.default_reader_settings'));
         setAction(null);
     }, []);
 
@@ -33,7 +35,7 @@ export default function DefaultReaderSettings() {
 
     const setSettingValue = (key: keyof IReaderSettings, value: string | boolean) => {
         requestUpdateServerMetadata(metadata ?? {}, [[key, value]]).catch(() =>
-            makeToast('Failed to save the default reader settings to the server', 'warning'),
+            makeToast(t('reader.settings.error.label.failed_to_save_settings'), 'warning'),
         );
     };