Fix minor styling errors

[AdvancedCodingMonkey]

Some styling details have been lost during package upgrades. Find out why and fix the issues.

• Home page:
  • color of navbar link text should be (0,0,0,0.5) instead of (0,0,0,0.65)
  • GISAID svg logo not visible, currently replaced by png
• FAQ page:
  • text color in region switcher buttons should be white
• Per variant page
  • Sort by dropdown should be inline
  • Countries sidebar selection markers used to be orange, I like the new blue ones better though
• Cases page
  • Variants sidebar selection markers used to be orange, I like the new blue ones better though