Add support for Table in Markdown TextField

[Gsyltc]

Describe the problem to be solved

Hello,

Would it be possible to add table support in text fields as markdown.

Currently, the rendering for a table remains "textual".
The table is not rendered correctly.

Thanks

Describe the solution you would like

No response

[drorsnir]

As far as I can tell, Grist currently uses marked, which supports tables by default, but gfm: false is set in MarkdownTextBox.ts. I couldn't find anything in the comments or commit history except for "A minimal subset of the
Markdown specification is currently supported", which doesn't tell me why, of course.

To be really clear, here's a minimal test case:

1. Add New -> New Empty Table
2. Set "Cell Format" to Markdown for column A
3. Paste a basic table:

| First Header  | Second Header |
| ------------- | ------------- |
| Content Cell  | Content Cell  |
| Content Cell  | Content Cell  |

4. The table isn't rendered: