feat: add some formatting and a better diagram for NGINXaaS DR.

[kuthiala]

Proposed changes

Got feedback to have the terraform code in collapsible sections and improve the diagram to show the connections between the secondary deployment and the upstreams better. Also fixed a spelling error.

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[amudukutore]

• The diagram changes look good to me.
• I like putting the code blocks into expandable sections.

Looks like some of the steps are missing now due to the expandable sections. Okay to merge once that is fixed.