docs: introduce agentic skills for OTel.io docs workflows (#9397)

[LoveChauhan-18]

PR Description

• I have read and followed the Contributing docs, especially the "First-time contributing?" section.
• This PR has content that I did not fully write myself.
  • I used AI and I have read and followed the Generative AI Contribution Policy.
• I have the experience and knowledge necessary to understand, review, and validate all content in this PR.¹

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This PR introduces an agentic skills catalog in the .agents/skills directory, as proposed in #9397. These skills are structured Markdown files that enable AI coding agents to automate common documentation workflows within the opentelemetry.io repository.

Initial Skills Added:

1. setup-localization.md: Automates the onboarding process for new localizations, including Hugo configuration updates and drafting the kickoff issue.
2. review-content.md: Provides a standardized checklist and command set for reviewing content against the OTel style guide and site-wide linting rules.
3. new-page-scaffold.md: Automates the creation of new documentation pages with correct frontmatter and weight calculations.

These skills are designed to improve the contributor experience for those using AI-assisted tools while maintaining compliance with project standards and automation requirements.

Fixes #9397

Footnotes

1. Yes, I can answer maintainer questions about the content of this PR, without using AI. ↩

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: LoveChauhan-18 / name: Love Kumar Chauhan (8d4a32d)
• ✅ login: otelbot[bot] / name: otelbot (87d6c60)

[LoveChauhan-18]

Hi, just checking in — please let me know if any changes are needed from my side. Happy to update if required. Thanks!

[theletterf]

+CC @vitorvasc

[vitorvasc]

/fix:format

[otelbot-docs]

✅ fix:format applied successfully in run 23659108977.