Mark ScriptSet.Has as const.

src/Battling/ScriptHandling/ScriptSet.hpp

@@ -55,7 +55,7 @@ namespace CreatureLib::Battling {
             _lookup.clear();
         }
 
-        bool Has(const std::string& key) {
+        bool Has(const std::string& key) const {
             auto find = _lookup.find(key);
             return find != _lookup.end();
         }