docs: Restructure website to improve UX

[aklinker1]

• Move entrypoint docs to own navigation item
• Merge guide and get-started into guide
• Split API reference into config, CLI, and JS APIs
• Generate CLI API reference
• Add redirection rules so old links still work

[netlify]

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[codecov]

Codecov Report

Merging #149 (43ff2de) into main (6342f59) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #149   +/-   ##
=======================================
  Coverage   85.26%   85.26%           
=======================================
  Files          61       61           
  Lines        4615     4615           
  Branches      423      426    +3     
=======================================
  Hits         3935     3935           
  Misses        680      680           

Files	Coverage Δ
src/client/createContentScriptUi.ts	100.00% <100.00%> (ø)

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