Add onTap callback on file preview list

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Package/Plugin version

4.1.0

### What you'd like to happen

```Markdown
Provide an onTap callback in the File Previewer widget. It will be useful in case of viewing file after uploading.

Usecase:
lets assume a user upload multiple files (pdf). As its not possible to preview pdf file we can provide a callback where we get a Platform file as argument. And using callback we can open file using external package.
```

### Alternatives you've considered

_No response_

### Aditional information