index.js: use public instead of protected OSMD accessors (more typescript friendly)

demo/index.js

@@ -956,8 +956,8 @@ import { TransposeCalculator } from '../src/Plugins/Transpose/TransposeCalculato
         function initialize() {
             timingSource.reset();
             timingSource.pause();
-            timingSource.Settings = osmd.sheet.playbackSettings;
-            playbackManager.initialize(osmd.sheet.musicPartManager);
+            timingSource.Settings = osmd.Sheet.playbackSettings;
+            playbackManager.initialize(osmd.Sheet.musicPartManager);
             playbackManager.addListener(osmd.cursor);
             playbackManager.reset();
             osmd.PlaybackManager = playbackManager;
@@ -967,7 +967,7 @@ import { TransposeCalculator } from '../src/Plugins/Transpose/TransposeCalculato
                 const instr = playbackManager.InstrumentIdMapping.getValue(instrId);
                 playbackControlPanel.addVolumeTrack(instr.Name, instrId, instr.Volume * 100);
             }
-            playbackControlPanel.bpmChanged(osmd.sheet.DefaultStartTempoInBpm);
+            playbackControlPanel.bpmChanged(osmd.Sheet.DefaultStartTempoInBpm);
         }
 
         function showControls() {