docs: new docs

[markov00]

Summary

This PR adds a general overview about the elastic-charts internal architecture and the overall usage and logic.

Mostly generated by AI

Checklist

• The proper chart type label has been added (e.g. :xy, :partition)
• The proper feature labels have been added (e.g. :interactions, :axis)
• All related issues have been linked (i.e. closes #123, fixes #123)
• New public API exports have been added to packages/charts/src/index.ts
• Unit tests have been added or updated to match the most common scenarios
• The proper documentation and/or storybook story has been added or updated
• The code has been checked for cross-browser compatibility (Chrome, Firefox, Safari, Edge)
• Visual changes have been tested with light and dark themes

[elastic-datavis]

⏳ Pending Deployment (build#5293) - d95c1e8

• ⏳ Storybook
• ⏳ e2e server
• ⏳ Playwright VRT report
• ⏳ Playwright A11Y report

[cla-checker-service]

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[markov00]

buildkite test this