fine tune scrobble conditions per LastFM API.

[jesseward]

Adhering to notes at https://www.last.fm/api/scrobbling#when-is-a-scrobble-a-scrobble

• The track must be longer than 30 seconds.
• And the track has been played for at least half its duration, or for 4 minutes (whichever occurs earlier.)

Github issue: https://github.com/jesseward/jellyfin-plugin-lastfm/issues/27