Add walkthrough video for APIOps CLI usage and configuration system

## Summary

Create and embed a walkthrough video in the documentation that demonstrates how to use APIOps CLI end-to-end, with particular focus on the configuration system.

## Proposed Content

The video should cover:

1. **Getting Started** — Installing the CLI, running `apiops init`, and scaffolding a repo
2. **Identity Setup** — Connecting GitHub/Azure DevOps to Azure via OIDC
3. **First Extraction** — Running `apiops extract` and reviewing the output
4. **Configuration Deep-Dive**
- Filter configuration (include/exclude APIs, resources)
- Publishing override configuration (per-environment overrides)
- Placeholder/token syntax for secrets (`{#[TOKEN_NAME]#}`)
- Environment-specific configuration files
5. **Publishing** — Running `apiops publish` and verifying changes in APIM
6. **CI/CD Integration** — How the scaffolded GitHub Actions / Azure DevOps pipelines work

## Acceptance Criteria

- [ ] Video is recorded and published (YouTube or similar)
- [ ] Video is embedded/linked in the documentation site
- [ ] Documentation page includes timestamps or chapter links for easy navigation
- [ ] README or docs index links to the video