docs: add missing callback options to events documentation table

[Copilot]

The "Available Callback Options" table was missing six callback functions added in commit 48531fc.

Changes:

• Added onAddRow, onAddColumn, onAddField to documentation table
• Added onRemoveRow, onRemoveColumn, onRemoveField to documentation table

These callbacks follow the same pattern as existing onUpdate* callbacks but fire when components are added or removed rather than updated.

const editor = new FormeoEditor({
  events: {
    onAddRow: (evt) => console.log('Row added:', evt.detail),
    onRemoveField: (evt) => console.log('Field removed:', evt.detail)
  }
})

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.

[kevinchappell]

lgtm

[Copilot]

Pull Request Overview

This PR addresses feedback from PR #411 by adding documentation for six missing callback options related to adding and removing rows, columns, and fields in the events system.

• Adds onAddRow, onAddColumn, onAddField callback documentation
• Adds onRemoveRow, onRemoveColumn, onRemoveField callback documentation

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

[nitpick] The ordering of these callback options doesn't match the pattern used in the "Available DOM Events" section below (lines 81-90). For consistency, consider grouping by component type instead of by operation type.

For example:

| `onUpdateRow`        | Function | Fires when row is updated                |
| `onAddRow`           | Function | Fires when row is added                  |
| `onRemoveRow`        | Function | Fires when row is removed                |
| `onUpdateColumn`     | Function | Fires when column is updated             |
| `onAddColumn`        | Function | Fires when column is added               |
| `onRemoveColumn`     | Function | Fires when column is removed             |
| `onUpdateField`      | Function | Fires when field is updated              |
| `onAddField`         | Function | Fires when field is added                |
| `onRemoveField`      | Function | Fires when field is removed              |

This would match the DOM Events table structure and make it easier for users to find related callbacks.

Suggested change

	| `onUpdateColumn` | Function | Fires when column is updated |
	| `onUpdateField` | Function | Fires when field is updated |
	| `onAddRow` | Function | Fires when row is added |
	| `onAddColumn` | Function | Fires when column is added |
	| `onAddField` | Function | Fires when field is added |
	| `onRemoveRow` | Function | Fires when row is removed |
	| `onRemoveColumn` | Function | Fires when column is removed |
	| `onAddRow` | Function | Fires when row is added |
	| `onRemoveRow` | Function | Fires when row is removed |
	| `onUpdateColumn` | Function | Fires when column is updated |
	| `onAddColumn` | Function | Fires when column is added |
	| `onRemoveColumn` | Function | Fires when column is removed |
	| `onUpdateField` | Function | Fires when field is updated |
	| `onAddField` | Function | Fires when field is added |