Link container requires rel type

[danielpeintner]

The following code

WoT.produce({
	...
	links: [ {
		href: "https://www.thingweb.io/img/favicon/favicon.png",
		sizes: "16x14",
		// rel: "icon", // required to succeed
	} ],
	...
}

fails with

Error: Cannot produce ExposedThing because " + Thing Description JSON schema validation failed:
should NOT be valid
should have required property 'rel'
should match exactly one schema in oneOf

This should NOT be the case since rel is optional. see https://w3c.github.io/wot-thing-description/#link