Product add related_products has_part

[rduyme]

Hi,
In https://skg-if.github.io/interoperability-framework/docs/research-product.html#related_products

Could we add inverse relation of "is_part_of" => has_part

 "related_products": {
        "cites": ["product_2", "product_3", "product_4"],
        "is_supplemented_by": ["product_7", "product_8", "product_9"],
        "is_documented_by": ["product_10", "product_13"],
        "is_new_version_of": ["product_10", "product_13"],
        "is_part_of": ["product_11"]
    }

Request from Raul for RoHub/Ro-crate mapping