Adding test case to prove existence of <svg:title>

[svanteschubert]

Adding test case to prove existence of svg:title after a round-trip (loading & saving the test file from #294) The stated problem could not be reproduced. Even when loaded and saved via LibreOffice the svg:title was not replaced by a svg:desc.

Version: 7.5.6.2 (X86_64) / LibreOffice Community Build ID: f654817fb68d6d4600d7d2f6b647e47729f55f15 CPU threads: 8; OS: Windows 10.0 Build 19045; UI render: Skia/Raster; VCL: win Locale: de-DE (de_DE); UI: de-DE Calc: CL threaded

This PR might close #294 - but we might as well neglect both.