fix(spells): backfill casting times for all imported spells

data/spells/read_magic.json

@@ -5,6 +5,7 @@
   "range": "personal",
   "save": "none",
   "base_dc": 10,
+  "cast_time": "standard",
   "effects": [],
   "description": "A cantrip: you can decipher magical inscriptions on objects that would otherwise be unintelligible, at one page per minute, and you can thereafter read that particular writing without the spell. Duration 10 min./level. No combat effect; reading magical writing is not modeled by the engine."
 }