Website: update links

[ch1bo]

• The website should link to the development tracker: https://engineering.iog.io/leios
• Put "Research & Development" section (in "Development") into context:
  • This was the workflow and areas during R&D
  • Most of it is still relevant, but roadmap and what we do is different
  • Artifacts like simulators and cost estimators are likely outdated
  • Also indicate that on the drop down
• Migrate or remove the "weekly updates" as there are no weekly updates (anymore). Maybe keep a link to them as a "News" blog in the footer, but only if we have semi-regular content.