Improve average color algorithm in media player

[martonborzak]

Expected Behavior or Design

The background color of the media player card perfectly matches the image.

Current Behavior or Design

Sometimes the background color is a bit off.

Detailed Description and Additional Information

The new Home Assistant media player card does a good job at this: https://github.com/home-assistant/frontend/blob/dev/src/panels/lovelace/cards/hui-media-control-card.ts

[martonborzak]

Better results with the following:

• scale image down to 1x1 pixel
• measure color of that pixel
• adjust according to lightness