#723 Add Astro porfolio guide to docs

[Polleps]

PR Checklist:

• Link to related issues: closes Astro + Atomic #723, closes Improve @tomic/lib search API #840, closes @tomic/cli Timestamp type mapping is incorrect #837, closes @tomic/cli should give clear error when trying to generate types from a non ontology resource #831, closes @tomic/cli crashes when generating ontologies while the output folder doesn't exist #830
• Add changelog entry linking to issue, describe API changes
• Add tests (optional)
• (If new feature) add to description / readme

TODO:

• Update JS parts for new API (no store etc)