Docs: Add example prompts for GitLab Duo Chat/Code Suggestions

What does this MR do?

GitLab Duo adoption requires practical, hands-on examples for our customers. This MR collects the learnings from FY24 and FY25 blog posts, recorded learning lessions in the GitLab Duo Coffee Chat gitlab-com/marketing/developer-relations/developer-advocacy/developer-advocacy-meta#375 and customer feedback into the documentation.

1. Add more examples to GitLab Duo Chat use cases, learned through the GitLab Duo Coffee Chat series
   1. /refactor practical examples
   2. /tests additional practical examples
   3. /explain practical examples from own workflows
   4. Add more examples for generating CI/CD configuration.
   5. Additional follow-up question example with C#
   6. New section: Ask about errors focussing on programming language errors, compiler error messages, etc. which is super helpful in the context as developer.
2. Introduce GitLab Duo examples documentation page
   1. Add story examples from GitLab Duo Coffee Chat series, which combine the power of all GitLab Duo features
   2. Link to YouTube recording resources
   3. Development: C#, C++
   4. Explain and resolve a vulnerability
   5. Solving a problem with Duo Chat Beta
   6. Contribute to GitLab using GitLab Duo
3. Introduce a Code Generation Prompts section in the new examples docs page
   1. Collect multi-line prompt generation examples for ~10 programming languages
   2. More to come from learnings in future GitLab Duo Coffee Chats and DevRel content, this is the first iteration.

All resources link back to YouTube, blog posts and projects maintained by the Developer Relations team.

Related issues

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