Use CSS style attributes for top level svg node

Change-Id: I1f1958e0e03868167a65a2186f955a085676f9d9
Reviewed-on: https://gerrit.libreoffice.org/6563
Reviewed-by: Christina Roßmanith <ChrRossmanith@web.de>
Tested-by: Christina Roßmanith <ChrRossmanith@web.de>