format: revealjs: pipe table renders as [Table] placeholder

[cderv]

Pipe tables in a format: revealjs document show as [Table] in the hub preview. The Table AST node has no renderer in the React pipeline — renderBlock in ReactAstSlideRenderer.tsx has no case 'Table'.

Minimal example:

---
format: revealjs
---

## My slide

| Col 1 | Col 2 |
|---|---|
| A | B |

Expected: rendered table. Actual: [Table].

Likely affects format: q2-slides too since both use renderBlock from the same file.

[cscheid]

We have many default components in q2-preview; this is probably a matter of organizing our components in these React formats such that all nodes like strong, emph, subscript, div, span, link, table, etc are rendered with the same components as q2-preview.