Doc: replace line numbers with snippets

Task-number: QTBUG-32109

Change-Id: Ifd34e0de579b1dfb1b08cf3d2646960d62f9d9eb
Reviewed-by: Sze Howe Koh <szehowe.koh@gmail.com>
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>