fix(sb3_definitions): allow sprites to be named 'stage' or 'Stage'

#49

Author: kchadha

lib/sb3_definitions.json

@@ -347,8 +347,7 @@
             "description": "Description of property (and/or property/value pairs) for sprites.",
             "properties": {
                 "name": {
-                    "type": "string",
-                    "not": {"enum": ["Stage", "stage"]}
+                    "type": "string"
                 },
                 "isStage": {
                     "type": "boolean",