Allow more primitives (boolean/number/string)

E.g. in ImageObject:

• isAccessibleForFree should be allowed to be a boolean primitive
• width and height should be allowed to be a number primitive
• author and contentLocation should be allowed to be a string primitive

Related: https://github.com/google/schema-dts/issues/19

[Eyas]

For Booleans, to save backwards compatibility, a good shape would be:

enum BooleanEnum {
    True = "https://schema.org/True",
    False = "https://schema.org/False"
}
/** Boolean: True or False. */
export type Boolean = true | false | BooleanEnum;
export const Boolean = {
  True: BooleanEnum.True as const,
  False: BooleanEnum.False as const,
}

So you can use:

• Boolean.True,
• Boolean.False, as well as true and false.

[Eyas]

Hm. Note that ImageObject doesn’t always work as a string, for example:

https://lists.w3.org/Archives/Public/public-schemaorg/2019Nov/0003.html

Structured Data Testing Tool rejects when “logo” is set to a string, requiring an ImageObject set explicitly.