[Feature Request]: Header line for simple table

[steffenrapp]

Description

Currently the simple table doesn’t support a header line. Lines can only be formatted manually.
Header lines of imported markdown tables are currently being ignored.

Use case

No response

Anything else?

No response

Are you willing to submit a PR?

• Yes I'd like to help by submitting a PR!

[affine-issue-bot]

Issue Status: 🆕 *Untriaged

*🆕 Untriaged

The team has not yet reviewed the issue. We usually do it within one business day.
Docs: https://github.com/toeverything/AFFiNE/blob/canary/docs/issue-triaging.md

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