Fix/458679

[anastasiya29]

Fix prop-types for errorComponent (this is a Placeholder prop in the react package)

Motivation

This fixes a bug where passing a custom error component via the errorComponent prop (as described in the docs) caused an "Invalid prop" error.

How Has This Been Tested?

Unit tests added.
Manual tests on react sample app.

1. Create a new CustomError component
2. Update Layout.js to pass a react component to the errorComponent prop to Placeholder <Placeholder errorComponent={CustomError} />
3. Verify that Home page renders without errors in disconnected and in EE
4. Update ContentBlock component to throw an error
5. Verify that CustomError is rendered on Home page instead of ContentBlock
6. Update Layout.js to pass a renderProp function to the errorComponent prop to Placeholder <Placeholder errorComponent={() => <div>Error</div>} />
7. Verify that "Error" is rendered on Home page instead of ContentBlock

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update (non-breaking change; modified files are limited to the /docs directory)

Checklist:

• [ x] I have read the Contributing guide.
• [ x] My code follows the code style of this project.
• [ x] My code/comments/docs fully adhere to the Code of Conduct.
• My change is a code change and it requires an update to the documentation.
• My change is a documentation change and it requires an update to the navigation.

[ambrauer]

Just the one comment re: coverage, and appears there may be linting errors based on the failed checks? Otherwise looks good to me.

[ambrauer]

Also, should this fix be mentioned in doc release notes?