Add support for content rating to more sources

[Luna712]

Some such as Pusatfilm should support it by setting contentRating to extract the rating field if present from the html, I'm unsure if it's possible for ones like DutaMovie but if it is, that one would be quite nice.

Additionally I've noticed on DutaMovie in particular extracting the "Synopsis" doesn't always work, even though it is is present in the HTML on the dutamovie21 website, on CloudStream it just says "Synopsis:" but without any content.