[tracking ticket] docs update

Ask: docs are half as long

Eric:
- [ ] update messaging on welcome page: https://use-fireproof.com/docs/welcome/
- [ ] Consider removing code snippets since that reads like a quickstart
- [ ] how do we want the concept guide to fit into the narrative: https://use-fireproof.com/docs/category/concept-guide

Marty:
1. update technical details on:
- [ ] P0: quickstart: https://use-fireproof.com/docs/getting-started
- [ ] P0: react tutorial: https://use-fireproof.com/docs/react-tutorial
- [ ] P1: https://use-fireproof.com/docs/solid-tutorial (or consider removing for now, there is a lot of surface area to the docs)