docs: initialise Argo CD app of apps documentation

[hairmare]

Description

This is the first part of the overarching changeset needed to properly document our -apps suffixed Argo CD app-of-apps charts as requested in #84.

• Splits Argo CD app-of-apps charts into their own main README section (demo)
• Adds initial docs/argocd-app-of-apps.md file (demo)
• cleanup README to make all tables look nice when view through github (demo)

After merging this, the docs/argocd-app-of-apps.md file can be collaboratively edited to adress the remaining tasks in #84, some of which will need further refinement before we are ready to document them.

Issues

• [*-apps] We need usage docs for argoconfig and *-apps charts #84

Checklist

• I updated the version in Chart.yaml
• I updated applicable README.md files using pre-commit run -a
• I documented any high-level concepts I'm introducing in docs/ ✅
• If I updated a dependency tool, or app, this PR contains a short summary of the changes I'm pulling
• CI is currently green and this is ready for review
• I am ready to test changes after they are applied and released