Can't upload .vsix file

### Is there an existing issue for this?

- [x] I have searched the existing issues

### OS/Web Information

- Web Browser: Edge
- Local OS: macOS
- Remote OS: Ubuntu
- Remote Architecture: x86_64
- `code-server --version`: v4.96.4

### Steps to Reproduce

1. Open code-server
2. Drag a `.vsix` file and drop it

### Expected

Upload successfully

### Actual

Loading forever

### Logs

```shell

```

### Screenshot/Video

### Does this bug reproduce in native VS Code?

This cannot be tested in native VS Code

### Does this bug reproduce in GitHub Codespaces?

No, this works as expected in GitHub Codespaces

### Are you accessing code-server over a secure context?

- [x] I am using a secure context.

### Notes

I have tried on both http/https
It works normally with other type of file