Enhance writing_exporters.md: Add actionable examples, checklists, and improved structure

Description

Proposal:

I would like to significantly improve the writing_exporters.md documentation by adding concrete code examples, clarifying best practices, and introducing a more actionable structure for new and experienced exporter authors.

Motivation

The current writing_exporters.md is comprehensive but can be dense for newcomers and lacks practical, ready-to-use examples in several key sections. Given that this document is a primary reference for anyone building Prometheus exporters, improving its clarity and usability will have a high impact on the community and ecosystem.

Proposed Improvements

• Add concrete code examples for:
  • Types & Labels (clarifying exporter vs. application labels)
  • Help strings (with troubleshooting context)
  • Scheduling (why exporters should not scrape on their own timers)
  • Exporter landing pages (minimal HTML example)
• Introduce a quick-start checklist at the end for new exporter authors.
• Clarify and expand best practices with before/after code snippets.
• Improve document structure for easier navigation (e.g., section summaries, cross-links to related docs).
• Add a troubleshooting section for common mistakes and anti-patterns.

Implementation Plan

1. Refactor the document to group related concepts and add section summaries.
2. Add new and improved code examples in Go (and/or pseudo-code where appropriate).
3. Insert a quick-start checklist and a “common mistakes” section.
4. Cross-link to related documentation (e.g., instrumentation.md, naming.md).
5. Solicit feedback from exporter maintainers and users for further improvements.

Refrences

[current_structure] https://prometheus.io/docs/instrumenting/writing_exporters/
[expected} https://prometheus.io/docs/prometheus/latest/getting_started/
[expected (even better)] https://kubernetes.io/docs/tasks/debug/debug-cluster/resource-metrics-pipeline/

Request for Feedback

• - Would maintainers and the community be open to a PR with these improvements?
• - Are there any specific pain points, requests, or recent exporter patterns you would like to see addressed in this update?

If approved, I will submit the changes as a single, well-structured PR with clear commit history and before/after documentation diffs.

Start with writing_exporters.md and compare its current structure with instrumentation.md and naming.md. Add the proposed Go or pseudocode examples, section summaries, cross-links, quick-start checklist, and troubleshooting content, then verify that the document is easier to navigate and actionable for exporter authors.