Add wake word to xmini-c3 (#730)

* esp-hi: MCP protocol is not ready yet

* Add wake word to xmini-c3

main/audio_processing/no_wake_word.h

@@ -0,0 +1,31 @@
+#ifndef NO_WAKE_WORD_H
+#define NO_WAKE_WORD_H
+
+#include <vector>
+#include <functional>
+#include <string>
+
+#include "wake_word.h"
+#include "audio_codec.h"
+
+class NoWakeWord : public WakeWord {
+public:
+    NoWakeWord() = default;
+    ~NoWakeWord() = default;
+
+    void Initialize(AudioCodec* codec) override;
+    void Feed(const std::vector<int16_t>& data) override;
+    void OnWakeWordDetected(std::function<void(const std::string& wake_word)> callback) override;
+    void StartDetection() override;
+    void StopDetection() override;
+    bool IsDetectionRunning() override;
+    size_t GetFeedSize() override;
+    void EncodeWakeWordData() override;
+    bool GetWakeWordOpus(std::vector<uint8_t>& opus) override;
+    const std::string& GetLastDetectedWakeWord() const override;
+
+private:
+    AudioCodec* codec_ = nullptr;
+};
+
+#endif