Move image files

[circumspect]

• Images make up the bulk of the repository's size (at time of writing, nearly half a gigabyte)
• The size of the repository scales with the number of supported languages multiplied by the number of cards
• Not only does Github limit the max size a repository can have, but large repos take longer to clone

Proposed solution: create separate repositories for each language, containing both the images and the localization file for that language

[circumspect]

Adding a metadata file for cards could also allow people to upload custom expansions as repositories

[circumspect]

Non-card resources (posters, game guide, character sheet) should probably have per-language repos as well. Bot localization text files should stay here. Translated cards can be treated as expansions