fix: add missing localization keys for sheet titles

- Add DS4.ActorSheet localization key ("Aktorbogen" / "Actor Sheet")
- Add DS4.ItemSheet localization key ("Itembogen" / "Item Sheet")

These keys are used in the get title() methods of DS4ActorSheet and DS4ItemSheet
to display properly localized sheet window titles instead of showing the raw
localization key strings.

Both keys are placed logically near other Actor/Item-related localization entries
for consistency.

lang/de.json

@@ -184,7 +184,9 @@
   "DS4.EffectFactor": "Faktor (wie oft der Effekt angewendet wird)",
   "DS4.EffectFactorAbbr": "F",
   "DS4.ActorName": "Name",
+  "DS4.ActorSheet": "Aktorbogen",
   "DS4.ActorImageAltText": "Bild des Aktors",
+  "DS4.ItemSheet": "Itembogen",
   "DS4.ActorTypeCharacter": "Charakter",
   "DS4.ActorTypeCreature": "Kreatur",
   "DS4.Attribute": "Attribut",

lang/en.json

@@ -184,7 +184,9 @@
   "DS4.EffectFactor": "Factor (the number of times the effect is being applied)",
   "DS4.EffectFactorAbbr": "F",
   "DS4.ActorName": "Name",
+  "DS4.ActorSheet": "Actor Sheet",
   "DS4.ActorImageAltText": "Image of the Actor",
+  "DS4.ItemSheet": "Item Sheet",
   "DS4.ActorTypeCharacter": "Character",
   "DS4.ActorTypeCreature": "Creature",
   "DS4.Attribute": "Attribute",