fdo#62281 Add a title to the About dialog

Change-Id: Idc9d9631dbb4990f878ee2f64b0f6fa36973307b
Reviewed-on: https://gerrit.libreoffice.org/11598
Reviewed-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>
Tested-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>