docs: clarify Hugo linkTitle guidance

[Jaegeonyoon]

Refs #1834

Changes

Clarified the Hugo front-matter section in CONTRIBUTING.md.

The old text explained that new Markdown files should have linkTitle, but it did not say much about how contributors should actually choose one. This update makes the guidance more practical:

• linkTitle is a short version of the page title shown in the website's left side navigation
• contributors should prefer short sub-area names such as Spans, Metrics, or Resources
• linkTitle should be omitted when it would be identical to the page title
• title and heading capitalization should follow the OpenTelemetry documentation style guide

Important

Pull request acceptance is subject to the triage process as described in Issue and PR Triage Management.
PRs that do not follow the guidance above may be automatically rejected and closed.

Merge requirement checklist

• CONTRIBUTING.md guidelines followed.
• Links to prototypes or existing instrumentations (when adding or changing conventions)
• Disclose AI usage, see OTel GenAI policy:
  • no AI used
  • AI-assisted
  • bulk AI-generated
• I have the experience and knowledge necessary to understand, review, and validate all content in this PR.¹

Footnotes

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

[lmolkova]

@chalin can you please take a look when you have a moment? Thanks!

[chalin]

Thanks @Jaegeonyoon.

All: FYI, the original intent of the section "Hugo frontmatter" (which the PR edits) was to inform semconv authors about Hugo front-matter conventions -- especially since these were encoded via comments, which is non standard, but might soon change, see:

• #2971

[chalin]

👍