Fix the Dark Sight spell (CleverRaven#35850)

* Add Difficulty to Dark Sight

Was originally zero. Justifying the value chosen by the clairvoyance spell, which gives you instantaneous 1 turn vision on all tiles in the aoe based on level. Clairvoyance has difficulty 4. Whereas Dark Sight gives encumbrance-free light amp vision for the same amount of time as a magical light spell. Compared to the Magical Lamp spell which generates regular light at difficulty 2, for the same amount of time. Comparing the distance you gain in vision from light amp, difficulty 6 seems justified.

* Add max level and 100 mana cost to Dark Sight

Set it at 20, like every other spell. Made the mana cost equivalent to Magical Light.

data/mods/Magiclysm/Spells/classless.json

@@ -11,8 +11,10 @@
     "min_range": 1,
     "max_range": 1,
     "base_casting_time": 100,
-    "base_energy_cost": 400,
+    "base_energy_cost": 500,
     "energy_source": "MANA",
+    "difficulty": 6,
+    "max_level": 20,
     "min_duration": 100000,
     "max_duration": 1000000,
     "duration_increment": 2000