feat: adding new features for release MYATLAS-223

Following the discussion in MYATLAS-223.

Major

I've added the following:

• Renamed "Showcase" into "About us", and added a team page with the ATLAS Open Data team. If we want this functionality:
  • Need to add all of us!!
  • Should we also add the past members?
• Latest News section at the bottom of the homepage, with information about our python package and some recent news

Minor

• Added Manchester Uni to the map
• Shuffled the header to have About us, Get Started, Documentation, Data, Tutorials, FAQs, What's new, Contact us

Summary of tasks

Major changes

• Add an "About us" page
• Add Latest News
• Re-order tutorials and data sidebar

Minor changes

• Re-structure the header
• Re-structure "our values" (mosaic?)
• Replace pictures in the homepage with newer/different ones