Media: show thumbnails for images

[ildar170975]

Assume a folder with images is added to media sources:

homeassistant:
  media_dirs:
    images: /config/www/images

In /media-browser/browser/, when a folder contains images, no thumbnails are displayed:

To see an image, it must be selected:

Suggest to show thumbnails for images.

P.S. Also, it would be create to show thumbnails for music files like mp3 & flac from embedded properties.