ESLint: Enable @typescript-eslint/return-await rule

This ensures stack traces are helpful at the cost of a slightly
lower performance (one more tick in the event loop).

Fixes #838

Signed-off-by: David Mehren <git@herrmehren.de>

src/media/backends/filesystem-backend.ts

@@ -46,7 +46,7 @@ export class FilesystemBackend implements MediaBackend {
   async deleteFile(fileName: string, _: BackendData): Promise<void> {
     const filePath = this.getFilePath(fileName);
     try {
-      return fs.unlink(filePath);
+      return await fs.unlink(filePath);
     } catch (e) {
       this.logger.error(e.message, e.stack, 'deleteFile');
       throw new MediaBackendError(`Could not delete '${filePath}'`);