[Appdir] Sitemap for new setup

[KenAJoh]

Description

Can be tested at /dev/sitemap.xml.

• Moved the fragmented definitions of "hardcoded" routes to a single config that can be used by both sitemap and sidebar config.

Component Checklist 📝

• JSDoc
• Examples
• Documentation / Decision Records
• Storybook
• Style mappings (@navikt/core/css/config/_mappings.js)
• Component tokens (@navikt/core/css/tokens.json)
• CSS class deprecations (@navikt/aksel-stylelint/src/deprecations.ts)
• Exports (@navikt/core/react/src/index.ts and @navikt/core/react/package.json)
• New component? CSS import (@navikt/core/css/index.css)
• Breaking change? Update migration guide. Consider codemod.
• Changeset (Format: <Component>: <gitmoji?> <Text>. E.g. "Button: ✨ Add feature xyz.")

[changeset-bot]

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Latest commit: 7c20531

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