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/components/library/UpdateChecker.tsx

@@ -7,6 +7,7 @@ import Typography from '@mui/material/Typography';
 import client from 'util/client';
 import makeToast from 'components/util/Toast';
 import { IUpdateStatus } from 'typings';
+import { useTranslation } from 'react-i18next';
 
 interface IProgressProps {
     progress: number;
@@ -30,6 +31,8 @@ interface IUpdateCheckerProps {
 }
 
 function UpdateChecker({ handleFinishedUpdate }: IUpdateCheckerProps) {
+    const { t } = useTranslation();
+
     const [loading, setLoading] = useState(false);
     const [progress, setProgress] = useState(0);
 
@@ -39,7 +42,7 @@ function UpdateChecker({ handleFinishedUpdate }: IUpdateCheckerProps) {
             setProgress(0);
             await client.post('/api/v1/update/fetch');
         } catch (e) {
-            makeToast('Checking for updates failed!', 'error');
+            makeToast(t('global.error.label.update_failed'), 'error');
             setLoading(false);
         }
     };