Allow setting an override for `createdDate` in `PdfRendererBuilder`

In a similar fashion to this PR: https://github.com/danfickle/openhtmltopdf/pull/158, it would be dynamite to be able to specify/override the `createdDate` in the builder in the saem style as the `producer`.

My use case is to set some fixed `createdDate` value - there are cases when I want to generate a PDF with identical inputs and have a hash of the document remain fixed. While having a "true" `createdDate` value is useful in many cases, there are times (like in automated testing) where it would be useful to be able to hash documents, and be able to rely on there being no volatile, changing tags that might break the hash.