Playback position indicator displays when playing or paused

[nimau]

Scrubber / green cursor behaviour:

• The scrubber (green cursor) does not display initially
• The cursor is displayed when either: the voice message is played or; the waveform is tapped.
• Once the scrubber is displayed, it continues to display even when other voice messages are played.
• Once the message finishes playing, the cursor disappears.
• Dragging the scrubber moves it. The touch target is accurate to just the area around the scrubber/cursor.
• Hence, showing multiple scrubbers on different voice messages is okay
  • As multiple scrubbers can show, they can all be dragged
  • Tapping also moves the scrubber to different parts of the recording