Split apart ecosystem page, update sidebar, other website tweaks

[jackgerrits]

Why are these changes needed?

• Split ecosystem page
• Remove dropdown - replace with just gallery
• Renamed SDK -> API
• Automatic TOC generation on FAQ
• Redirect /docs

Related issue number

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://microsoft.github.io/autogen/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 35.69%. Comparing base (fcf14ee) to head (cdd4926).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1812   +/-   ##
=======================================
  Coverage   35.69%   35.69%           
=======================================
  Files          63       63           
  Lines        6625     6625           
  Branches     1454     1454           
=======================================
  Hits         2365     2365           
  Misses       4067     4067           
  Partials      193      193           

Flag	Coverage Δ
unittests	35.69% <ø> (ø)

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