Add basic architecture documentation

[j08lue]

All building blocks need docs based off of this template: https://github.com/EOEPCA/document-template and chained together into the main docs site via https://github.com/EOEPCA/docroot

Following up on

• Spike: Why and how to combine eoAPI and Stacture/Terravis to fulfil BB requirements #10

Document:

1. Why have we chosen this architecture?
2. Strengths and differences of the libraries
3. Benefits of making both libraries available in the building block
4. Pattern of integration

Acceptance criteria

• Decide on whether we'll have a dedicated repo for the Data Access BB helm charts
• Bootstrap Data Access BB docs in dedicated docs repo or helm charts repo
• @j08lue to start document / docs branch
• @constantinius to contribute

[j08lue]

Made a first push here:

• Add docs on architecture design #11

I just merged right away to start populating the docs, but it needs further revision and contribution. I'll organize that shortly.