Easier way to disable all rotation and pitch

@karimnaaji is already working on this.

Since Jul 9, 2021.

Sadly, most of the maps that I work on have no need for any 3D features or orientations other than north-up. But by default all these navigation features are enabled, which means eventually some poor user accidentally holds down control and gets very confused. Then I fumble through finding how to disable them all:

```
var map = new mapboxgl.Map({
...
pitchWithRotate: false,
dragRotate: false,
touchZoomRotate: false
).addControl(new mapboxgl.NavigationControl({ showCompass: false }), 'top-left');
```

Just a suggestion to consider making this easier, like maybe an option such as "fixedViewport: true" that would imply the others. Or just a note in the documentation explaining the above.