Improving compatibility with Doxygen v1.15.0 and higher 🔧

Fixed

• The last item in the new page outline panel is not hidden by the footer anymore (#197). Thanks to @parmi93 for reporting!
• Code fragments are now readable again in Doxygen v1.15.0 and higher (#199). Thanks to @ldclip for reporting and to @my1e5 and @fleckerbr for providing a fix!

Full Changelog: v2.4.1...v2.4.2