Improve validator coverage and add feature flag editor example

[SunnyDevendranadh]

Summary

Polishes Bloom’s public-readiness layer after PR #9 by expanding validator coverage, keeping docs aligned with the active rule registry, and adding a richer custom-editor example artifact.

Changes

• Adds 3 active validator rules:
  • responsive-images
  • no-empty-elements
  • no-inline-styles-except-root
• Adds a targeted fixture and test coverage for the new rules.
• Updates README and validator docs from 10 to 13 active rules.
• Fixes the stale bloom-validator/package.json description.
• Adds examples/feature-flag-editor-example.html as a custom-editor example with toggles, pending diff, and copy JSON/markdown actions.
• Removes inline style= usage from existing templates/examples so stricter validation remains clean.

Verification

• cd bloom-validator && npm test
  • 13/13 tests pass
• cd bloom-validator && npm run validate-all
  • 19/19 artifacts pass
• Placeholder scan over templates/ and examples/
  • clean
• Inline style scan over templates/ and examples/
  • clean