Remote images

[nagyrobi]

Consider reviewing esphome#4710 or implement something similar:

Two use cases here:

• display the coverart of a song, which can be retrieved from an attribute of a HA media player (accessible via http)*
• display a weather panel, without storing all the possible weather icons in flash (share them from HA's www directory via http)

*: http://ha_address:8123{{ state_attr('media_player.your_room','entity_picture') HA template serves the cover art picture, aka. http://ha_address:8123/api/media_player_proxy/media_player.your_room?token=XXX...