Move PN532OnTagTrigger to nfc::NfcOnTagTrigger (#3379)

esphome/components/nfc/automation.h

@@ -0,0 +1,17 @@
+#pragma once
+
+#include <string>
+#include "esphome/core/automation.h"
+
+#include "nfc.h"
+
+namespace esphome {
+namespace nfc {
+
+class NfcOnTagTrigger : public Trigger<std::string, NfcTag> {
+ public:
+  void process(const std::unique_ptr<NfcTag> &tag);
+};
+
+}  // namespace nfc
+}  // namespace esphome