Add troubleshooting content type guidelines

[alexandra5000]

Summary

This PR introduces a new "Troubleshooting" content type with detailed guidelines for creating effective troubleshooting pages in the Elastic documentation. Additionally, a template for troubleshooting pages is added. Updates to the content types index.md file are also made to include the new troubleshooting section.

Closes #115

Generative AI disclosure

To help us ensure compliance with the Elastic open source and documentation guidelines, please answer the following:

1. Did you use a generative AI (GenAI) tool to assist in creating this contribution?

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2. If you answered "Yes" to the previous question, please specify the tool(s) and model(s) used (e.g., Google Gemini, OpenAI ChatGPT-4, etc.).

Tool(s) and model(s) used:
Some edits with Claude Sonnet 4.5 using Cursor

[github-actions]

Vale Linting Results

Summary: 1 warning, 2 suggestions found

⚠️ Warnings (1)

File	Line	Rule	Message
contribute-docs/content-types/_snippets/templates/troubleshooting-template.md	137	Elastic.DontUse	Don't use 'Just'.

💡 Suggestions (2)

File	Line	Rule	Message
contribute-docs/content-types/_snippets/templates/troubleshooting-template.md	130	Elastic.Wordiness	Consider using 'all' instead of 'all of '.
contribute-docs/content-types/troubleshooting.md	23	Elastic.WordChoice	Consider using 'can, might' instead of 'may', unless the term is in the UI.

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[github-actions]

🔍 Preview links for changed docs

• contribute-docs/content-types/troubleshooting.md
• contribute-docs/content-types/index.md

[theletterf]

Yay! First review pass

[shainaraskas]

was the old guidance mined before this PR was created? lots in there, especially around error messages

https://stunning-adventure-qrvr1k2.pages.github.io/content-types/troubleshooting/type-troubleshooting/

[alexandra5000]

@shainaraskas Thanks! I made some updates based on the old guide.

[KOTungseth]

This is a strong foundation with clear intent, well aligned with how Elastic users consume troubleshooting content, and appropriately prescriptive.

I left some suggestions for making the content more operational for contributors.

[leemthompo]

This looks great! Nice work @alexandra5000, I'm no troubleshooting expert so I'm not really qualified to approve this, but I think with @theletterf and @KOTungseth's suggestions this will be in good shape

[shainaraskas]

fwiw, support was VERY passionate about us having this additional resources/contact/working with support boilerplate on entrypoints, especially because half of our troubleshooting content is in the support portal

https://stunning-adventure-qrvr1k2.pages.github.io/content-types/troubleshooting/

[alexandra5000]

@shainaraskas Very good point, thank you for reminding me about it. I even discussed adding a dedicated "Contact support" page to every troubleshooting folder/section. As of today, a dedicated page exists in some of them, so I included that info as well.