enhancement: additional card metadata to track related cards (matching art, story sets, etc)

[fernflower]

Data affected

• Card
• Set
• Serie
• Other
• new Data Type

Please explain in more details what idea you have

I'd like to propose an additional metadata field that would contain related cards information. This would make it possible to create a database of matching arts / story telling cards / cards-that-have-a-common-feature like Arven's lighthouse in the background or those staged in one location.

Something like:
data/Scarlet & Violet/Scarlet & Violet/151.ts:

	metadata: {
		collections: [
			{
				label: "HYOGONOSUKE",
				orientation: "grid",
				relatedCards: ["sv04.5-031", "sv03-008", "sv04-152", "sv02-042", "sv02-096", "sv04-030", "sv03-180", "sv04-091"]
			}
		]
	}

data/Sword & Shield/Evolving Skies/128.ts

	metadata: {
		collections: [
			{
				label: "Trail of Paint",
				relatedCards: ["swsh8-199", "swsh7-16", "swsh8-119"]
			}
		]
	}

There is a POC already if you'd like to see for yourself (there is a demo /related-cards endpoint and a cli oneliner to add new entries). Happy to contribute and tune that idea to your liking :)

Thanks for the awesome project anyway!