Doc how-to enable deployment slot in Bicep

[puicchan]

• Doc
• Blog

[puicchan]

Blog: https://devblogs.microsoft.com/azure-sdk/azd-app-service-slot/
Blog: https://devblogs.microsoft.com/azure-sdk/azd-appservice-swap/

[puicchan]

@alexwolfmsft

[alexwolfmsft]

Addressed in: https://github.com/MicrosoftDocs/azure-dev-docs-pr/pull/8783