Add a comment to explain the reason for the code

Author: m-kuhn

src/app/qgsmaptooldigitizefeature.cpp

@@ -211,6 +211,7 @@ void QgsMapToolDigitizeFeature::cadCanvasReleaseEvent( QgsMapMouseEvent *e )
       f.setGeometry( g );
       f.setValid( true );
 
+      // The snapping result needs to be added so it's available in the @snapping_results variable of default value etc. expression contexts
       addVertex( e->mapPoint(), e->mapPointMatch() );
 
       digitized( f );