Add official Dragonslayer sheet files

Added all required files for the official Dragonslayer Classic Fantasy RPG character sheet:


• dragonslayer.css – complete styling for all tabs and rolltemplates
• sheet.json – metadata, instructions, preview reference
• dragonslayer.jpg – sheet preview image for Roll20 directory

These files form the complete, sanctioned sheet approved by Greg Gillespie.

Dragonslayer/sheet.json

@@ -0,0 +1,9 @@
+{
+  "html": "dragonslayer.html",
+  "css": "dragonslayer.css",
+  "authors": "Bradley and Todd Antill",
+  "roll20userid": "759581",
+  "preview": "dragonslayer.jpg",
+  "instructions": "<b>This character sheet is designed for use with the Dragonslayer Classic Fantasy Role-Playing Game by Greg Gillespie.</b><br><br>\n\n<b>Notes</b><br>\n• This sheet includes one-click roll buttons for attacks, saving throws, thief skills, and class abilities. Rolls automatically calculate total to-hit, damage, and success or failure.<br><br>\n\n• Ability score modifiers are automatically calculated when ability scores are entered. Saving throws are calculated when class and level are entered.<br><br>\n\n• The sheet features a toggle that switches between the standard player-character sheet and a monster-style stat block.<br><br>\n\n• This is the official Dragonslayer Classic Fantasy RPG Roll20 sheet and will be compatible with future compendia.",
+  "legacy": true
+}