Add `The Drowned City`

[fspoettel]

⚠️⚠️⚠️ Don't interact with this PR if you don't want to get spoiled. ⚠️⚠️⚠️

This PR tracks the drowned city card spoilers and is a central place to discuss new card metadata. This PR is a work in progress.

New things with metadata impact:

• Investigator Agatha Crane has two investigator cards, each belonging to a different factions and with different deckbuilding.
  • Probably handle as separate cards. In contrast to parallels, there is no clear "default" to show over the other.
  • TBD: Add a field version_of to allow optional business logic for this special case.
• New card "type" specialist which limits investigator access by one or more traits and has a different frame.
  • Handle as faction_code: neutral, otherwise a lot of things break.
  • Use existingrestrictions field or add a field card_restrictions: [] to encode the access limitations.
  • TODO: Backport this for class weaknesses.
  • Maybe add an additional tag or field to denote as specialist card?