Custom scheduling (v3): add deck related info

[dae]

[Feature Request] Set Anki custom scheduling per deck/option

It’s only possible to provide a single block of code, but you can make it behave differently depending on the deck using a bit of a hack: if you add <div id=deck>{{Deck}}</div> to the card template, your custom scheduling code can extract the deck name from the DOM, and vary its behaviour as necessary.