docs: add cors docs

[namchuai]

Describe Your Changes

• Add CORS setting docs

Self Checklist

• Added relevant comments, esp in complex areas
• Updated docs (for bug fixes / features)
• Created issues for follow-up changes or refactoring needed

[github-actions]

Preview URL: https://71c6261a.cortex-docs.pages.dev

[gabrielle-ong]

Thank you so much @namchuai for the initial docs! Ill take it from here

• add to the CLI section. cortex config
• Move Configuration to API Server capabilities (with Log Levels)
  To merge this after epic: API and CLI to enable/disable CORS #1635 is merged (to dev / 1.0.2 release)