[Documentation] Create documentation for .json card format

[demilich1]

Having all cards outside the code as .json files is great, as it potentially allows users to create their own cards. However this is next to impossible in pratice at the moment, as there is no documentation about the format at all.

There should be a documentation covering all spells, triggers, value providers etc with all valid arguments.

[webadict]

I reordered the card keys in order for this to be more doable. I might reorganize the Spells so that keywords can be more easily identified and also used between spells, with an added bonus of reducing extraneous keys. Eventually, I might even write up documentation.