[dumpert] Fix extractor for redesign (#22428)

[jorams]

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• Bug fix
• Improvement
• New extractor
• New feature

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Description of your pull request and other information

This fixes the extractor for dumpert.nl, which broke with the recent redesign of the website. See also #22428.

Note that this also still supports old-style URLs, and even embed URLs which don't seem to be supported anymore.