feat: parse :icon-name: syntax in table cells

[Copilot]

Adds support for :icon-name: at the start of table cell content, emitting an icon node followed by a text node for any trailing content. Works in both header and body cells.

Changes

src/parser/transformer.ts

• In transformTable, cell text nodes are now tested against /^:([a-z-]+):\s*([\s\S]*)$/
• On match: pushes an icon node (props.name = captured name) and, if non-empty trailing text exists (trimmed), a text node
• Non-matching cells fall through unchanged

tests/parser.test.ts

• New "Icon in Table Cells" suite covering: icon + trailing text, icon-only, hyphenated names (:arrow-right:), header cells, and non-icon cells

Example

| Status | Item |
|--------|------|
| :check: Done | Task A |
| :x: Failed   | Task B |

Parses the first body cell as [{ type: 'icon', props: { name: 'check' } }, { type: 'text', content: 'Done' }].