add PROMPT_TARGET_IMMUNE to doc_holyday

Author: salvoilmiosi

src/effects/dodgecity/doc_holyday.cpp

@@ -9,6 +9,11 @@
 namespace banggame {
 
     prompt_string handler_doc_holyday::on_prompt(card_ptr origin_card, player_ptr origin, const card_list &target_cards, player_ptr target) {
+        if (origin->is_bot() && rn::all_of(target_cards, [&](card_ptr target_card) {
+            return target->immune_to(target_card, origin, {}, true);
+        })) {
+            return {"PROMPT_TARGET_IMMUNE", origin_card, target};
+        }
         return effect_bang{}.on_prompt(origin_card, origin, target);
     }