Tweaks for headers spacing

[Forkmen123]

I wasn't completely happy with the headers spacing and the font size of the title of the document, so I decided to change these.

Here was before my changes :

And after :

The changes are made so that in reading or editing mode, the spacing remains the same.

[clearlysid]

Thanks for submitting this! Imo the spacing is a bit too much now. In an ideal case we'd find a way to make both of the following situations look natural.

## A big heading

Some paragraph with lots of text.

### A slightly smaller heading

Another paragraph.

---

## A big heading

### A smaller heading

#### Even smaller heading

A paragraph.

both the segments above should be decently spaced^. Up for the challenge?