docs(docs): Update to latest docs builder, add architecture docs templates

[stevenj]

Description

This PR updates our docs to use the latest docs builder.
This means we no longer have to explicitly create the nav tree, it will be autogenerated from the markdown files in src.
It also enables the documentation building for ADRs which are part of the arc42 Architecture docs added in this PR.

Please confirm the following checks

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream module