Update README files to align with other Auth0 SDK repos and v1.0.0 release

[SurajThotakura]

Changes

• Root & Package READMEs: Transitioned from contributor-focused to public-facing. Standardized layouts (Quick Nav, Docs, Feedback), fixed broken Auth0 URLs, updated image assets, and added standard Auth0 footers.
• Example Apps (next-rwa, react-spa-*): * Streamlined setup by relying on the bootstrap script (removed manual CLI auth steps).
  • Added a manual configuration fallback guide (mandatory for private-cloud tenants).
  • Standardized the "Using Components" section across all examples.
  • Fixed shadcn specifics (corrected component install paths to components/auth0/, removed redundant init steps).
• React Package (packages/react): Corrected install commands. Added npm metadata and keywords to package.json.
• Core Package (packages/core): Updated description and added npm badges.
• CONTRIBUTING.md: Created new file to house the monorepo architecture and local dev workflows previously in the root README
• Added a gif in the root README to showcase our customization

References

• Auth0 Universal Components documentation: DOCS
• Auth0 SDK README conventions: auth0.js, nextjs-auth0

Testing

Just updates to READMEs

• This change adds unit test coverage
• This change has been tested on the latest version of the platform/language or why not

Checklist

• I have read the Auth0 general contribution guidelines
• I have read the Auth0 Code of Conduct
• All existing and new tests complete without errors

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.42%. Comparing base (a8b6c32) to head (1ada7d0).

Additional details and impacted files

@@           Coverage Diff            @@
##             main     #255    +/-   ##
========================================
  Coverage   89.42%   89.42%            
========================================
  Files         159      159            
  Lines       13325    13325            
  Branches     1435     1749   +314     
========================================
  Hits        11916    11916            
  Misses       1409     1409            

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