feat(frontend): add xlsx (QuivrHQ#3340)

# Description

Please include a summary of the changes and the related issue. Please
also include relevant motivation and context.

## Checklist before requesting a review

Please delete options that are not relevant.

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my code
- [ ] I have commented hard-to-understand areas
- [ ] I have ideally added tests that prove my fix is effective or that
my feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged

## Screenshots (if appropriate):

frontend/app/quality-assistant/AssistantTab/AssistantTab.tsx

@@ -23,7 +23,7 @@ interface AssistantTabProps {
   setSelectedTab: (tab: string) => void;
 }
 
-const FILE_TYPES = ["pdf", "docx", "doc", "txt"];
+const FILE_TYPES = ["pdf", "docx", "doc", "txt", "xlsx", "xls"];
 
 const useAssistantData = () => {
   const [assistants, setAssistants] = useState<Assistant[]>([]);