Add dc:date with metadata from site instead of now() example impl.: Literotica

[baalthasar]

The Literotica parser relied on fragile DOM selectors and did not support publication dates. Additionally, the “no Additional Metadata” option cleared site-provided tags during EPUB packaging.

This PR adds:

• extract Literotica author, publication date, description, and tags from Article JSON-LD
• retain DOM and meta-tag fallbacks for alternate/older markup
• add an editable publication-date metadata field
• write the original publication date to EPUB dc:date
• preserve site-provided metadata when external metadata is disabled
• add regression coverage for Literotica metadata and EPUB publication dates

[gamebeaker]

@baalthasar as is described here: CONTRIBUTING.md

Have you updated the "contributors" section of packages.json with your name? (and ideally email, so I can contact you easily.)
Have you updated the "Credits" section of readme.md with your name?

Do you want to add yourself?