Adds more natural default header option when inserting table columns

[tjramage]

Description

When inserting a new column to an existing table, the current implementation of the addColumn transform only allows for all table cells to be a header at once (TH) or none at all. However, most of the time, you usually want the top row of cells to remain as a table header and all other instances as standard TD cells.

This PR allows the flexibility for the header option to be more consistent with the current table row that we're iterating through when inserting a new column 🙂

To maintain backwards compatibility, I've made sure that this only happens if the header option is not set. If the header option is already configured when calling addColumn, then this will override the default behaviour for all table cell instances.

Checklist

• The new code matches the existing patterns and styles.
• The tests pass with yarn test.
• The linter passes with yarn lint. (Fix errors with yarn lint --fix.)
• The relevant examples still work: (Run examples with yarn docs.)

[changeset-bot]

🦋 Changeset detected

Latest commit: 56b2551

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 4 packages

Name	Type
@udecode/plate-table	Patch
@udecode/plate-table-ui	Patch
@udecode/plate	Patch
@udecode/plate-csv-serializer	Patch

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[tjramage]

Thanks @dylans! Looking forward to getting this merged in 👍

[zbeyens]

Thanks @tjramage !