* Reorder option descriptions in alphabetical order

* Add list of options for easier browsing

Create a list of all options at the top of the page to
make the option descriptions easier and quicker to find.
Each list entry is a link to its corresponding description.

* Fix broken link

Co-authored-by: Lily Acadia Gilbert <lily@informedk12.com>

This can be turned on via:

```python
JWTManager(app, add_context_processor=True)
```

or

```python
jwt.init_app(app, add_context_processor=True)
```

I did not make turning this on the default because it could be a
breaking change. Come the next major release I will likely change this
to be on by default.

Fixes #478

Follows suite of flask and cryptography packages.