docs: add ARCHITECTURE.md

[flavio]

Explain how the audit-scanner performs the scan.

Possibile improvements

1. Instead of doing Namespace auditing sequentially, allow for parallel auditing of namespaces. Expose a flag for that
2. Inside of a Namespace, keep auditing resources in parallel, but instead of hard coding the number of resources being audited in parallel, expose a flag for that
3. When auditing a specific resource (like a specific Pod), instead of evaluating each policy sequentially, evaluate them in parallel. Expose a flag for that

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.90%. Comparing base (038da59) to head (84ece12).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #285   +/-   ##
=======================================
  Coverage   70.90%   70.90%           
=======================================
  Files          11       11           
  Lines         976      976           
=======================================
  Hits          692      692           
  Misses        213      213           
  Partials       71       71           

Flag	Coverage Δ
unit-tests	70.90% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[flavio]

Merging, I've addressed all the comments. Thanks!