Implement documentationLinks validation to match Figma API

[svallory]

Original issue: react-figma#29

Simulate Error: in set_documentationLinks: Documentation links API takes a list of size 0 or 1

Assigning array with more than one elements documentationLinks throws an error:

Error: in set_documentationLinks: Documentation links API takes a list of size 0 or 1

How it should work?

API Doc: https://www.figma.com/plugin-docs/api/properties/nodes-documentationlinks/

Signature

documentationLinks: ReadonlyArray<DocumentationLink>

Remarks

This API currently only supports setting a single documentation link. To clear the documentation links, set to the empty list [].

NOTES

The error message may have changed (issue is from May 2021)