[Documentation] Add editable architecture diagrams

What does this PR do?
Adds architecture diagrams for Kubernetes and high-level design of Firefish to quickly get an idea of what will be deployed and how the pieces fit together. This also helps developers of future enhancements see where scalability improvements can be made e.g. splitting queue workers into an independently scalable microservice or optionally swapping out the queue mechanism entirely for alternatives like SQS for a specific deployment.
The diagram is an editable .svg file made with Draw.io.

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Thanks!