Vienna 3.5.3

What's new in this version:

- Fix crash with problematic feed
- Fix parsing of feeds without titles
- Use basic preemptive authentication to work around some servers which do not send 401 challenges
- Fix update of tabs color when window gains/loses focus
- Prevent Vienna from appearing among dedicated browser applications in System Preferences/General
- Fix usability problem with search box
- Add DuckDuckGo and Qwant among options for search box
- Fix Twitter option for search box
- Use https for searching
- Add support for dark mode to Credits
- Fix tooltips in folders tree
- Update Sparkle to 1.21.2, autorevision to 1.21