Update links & info; alt text on image

[samharp]

Made a few small changes to keep this document up to date:
 

• remove Microsoft AI Grants link as it now redirects to a different Microsoft tool (Planetary Computer)
  • according to a Microsoft press release, it was only going to be around for 5 years... sad face
• Add Planetary Computer link to Data and Metrics (a multi-petabyte of climate data?!?)
• add alt text to Reddit banner image
• remove empty link for "self-driving cars" to eliminate confusion of why the link didn't work
• add "carbon removal" to Emerging Technologies so the "self-driving cars" didn't sit in a list all by itself