[Feature Request] Also keep outline headers on top

I think it would be so helpful when viewing lisp files to also have the option to keep headings on top, so that at a glance you get a full glimpse of the context of where point is. The top-level heading would obviously be on top, with any subheadings beneath, and finally the relevant function title last. This means the number of lines required at the top would fluctuate as you move through the file, which hopefully wouldn’t be too hard to implement. An example of how it might look would be:

```
;;; Custom Variables
;;;; Appearance Variables
(defcustom var
```

Thank you so much for this package, and all of your wonderful packages!