Lavalink.py 4.0.7

Fixes

• Fix bad endTime check.
  • Additionally, raise minimum endTime duration to 1.

Additions

• Add LoadResult.selected_track convenience property.
• Add Client.get_source() convenience method.

Changes

• Raise original error in utils.timestamp_to_millis.
• Slight improvement to DefaultPlayer.play documentation to clarify the difference between it and BasePlayer.play_track.