Add getCurrentTrackArtworkURL() to spotify extension

[vjo]

Problem

I would love to be able to use track artwork in notification.

Here is a usage example:

  local track = hs.spotify.getCurrentTrack()
  local artist = hs.spotify.getCurrentArtist()
  local url = hs.spotify.getCurrentTrackArtworkURL()
  local image = hs.image.imageFromURL(url)
  hs.notify.new({title=track, subTitle=artist, contentImage=image }):send()

Solution

Introduce getCurrentTrackArtworkURL() function to spotify extension returning the URL of the artwork for the current track.

[github-actions]

This pull request does not contain a valid label. Please add one of the following labels: ['pr-fix', 'pr-change', 'pr-feature', 'pr-maintenance']