fix(docs): Update CDN usage example

[ChristianHamm]

Description

Update and rework the CDN usage example documentation.

Jira: STACKITCDN-1003

Checklist

• Issue was linked above
• Code format was applied: make fmt
• Examples were added / adjusted (see examples/ directory)
• Docs are up-to-date: make generate-docs (will be checked by CI)
• Unit tests got implemented or updated
• Acceptance tests got implemented or updated (see e.g. here)
• Unit tests are passing: make test (will be checked by CI)
• No linter issues: make lint (will be checked by CI)

[ChristianHamm]

@marceljk I've just addressed your points above. Feel free to take another look now 🙂

[ChristianHamm]

bump

[marceljk]

@ChristianHamm Sorry for the late response. The guide looks good to me and I approved it. I'll post it in our internal chat for the second review :)