Feature: Option to remove `| undefined` from optional prop types

[unional]

Problem

When using TypeScript's explicit optional property pattern (prop?: Type | undefined), react-docgen displays the type as union instead of showing the actual type.

This pattern is common in codebases using exactOptionalPropertyTypes: true in tsconfig, which requires explicit | undefined for optional properties.

Example

interface ButtonProps {
  onClick?: ((event: MouseEvent) => void) | undefined
  variant?: 'primary' | 'secondary' | undefined
  icon?: ReactNode | undefined
}

In Storybook's props table (using react-docgen), these all display as "union" instead of:

• (event: MouseEvent) => void
• 'primary' | 'secondary'
• ReactNode

Requested Feature

Add a parser option similar to react-docgen-typescript's shouldRemoveUndefinedFromOptional:

{
  shouldRemoveUndefinedFromOptional: true
}

When enabled, this would:

1. Detect optional properties (those ending with ?)
2. Strip | undefined from their type representation
3. Display the actual meaningful type instead of "union"

Prior Art

react-docgen-typescript has this feature via the shouldRemoveUndefinedFromOptional option:
https://github.com/styleguidist/react-docgen-typescript#parseroptions

Workaround

Currently, Storybook users must manually specify table.type.summary for every affected prop:

argTypes: {
  onClick: {
    table: { type: { summary: '(event: MouseEvent) => void' } }
  }
}

This is tedious and error-prone for large component libraries.

Environment

• react-docgen: latest
• TypeScript: 7.x with exactOptionalPropertyTypes: true
• Storybook: 10.x using reactDocgen: 'react-docgen'