[Documentation] Serializing Pipeline unclear

## Summary
On this page, it claims to serialize a pipeline, you use the following methods:
```
config = nlp.config
bytes_data = nlp.to_bytes()
```

and that you you must take care of storing both and then loading from disk.

However, it also appears that:
```
nlp.to_disk('directory_name')
```

coupled with:
```
spacy.load('directory_name')
```

works and this is a lot more simple. The code executes and I can call a built nlp object on text successfully.

## Questions

1. Does this approach actually work identically?
1. If so, can we update the documentation? The `nlp.config` and `to_bytes` seem like implementation details rather than the API for serializing?
2. I didn't see a mention on this page that you can load the persisted pipeline from disk with `spacy.load`, should this be added?

2. If this approach doesn't work, I think we should call this out and build a function/method that handles loading and saving to disk with a single call - this seems better than having to write your own disk persistence for the config and bytes object. What do you think?

Thanks!

## Which page or section is this issue related to?
https://spacy.io/usage/saving-loading