text: Title: Update the scale bar example for the latest API
  Body: ## 🧰 Task
  The scale bar example
  https://napari.org/dev/gallery/scale_bar.html
  
  Doesn't cover the latest scale bar API, which permits a lot more.
  It should be updated to include some of the new options:
  https://github.com/napari/napari/blob/0e01840c9237489acf238aec1d5cdaf9201ed640/napari/components/overlays/scale_bar.py#L10-L46
  
  
  Would be good to also update the docs, see:
  https://github.com/napari/docs/issues/38
  
  Motivation:
  User post on image.sc 
  https://forum.image.sc/t/increasing-font-size-and-repositioning-the-scale-bar/97972/3
  