Add `tempfile._TemporaryFileWrapper` to transport `file_classes`

`tempfile._TemporaryFileWrapper` is the return type of the (confusingly named) function `tempfile.NamedTemporaryFile`. As such it's a useful class for sending files via GraphQL:

```python
with NamedTemporaryFile as file:
    file.write(...)
    request = GraphQLRequest("...", variable_values={"file": file})
    ...
```
