Introduce cpu_frequency module

include/modules/cpu_frequency.hpp

@@ -0,0 +1,30 @@
+#pragma once
+
+#include <fmt/format.h>
+
+#include <cstdint>
+#include <fstream>
+#include <numeric>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "AButton.hpp"
+#include "util/sleeper_thread.hpp"
+
+namespace waybar::modules {
+
+class CpuFrequency : public AButton {
+ public:
+  CpuFrequency(const std::string&, const Json::Value&);
+  ~CpuFrequency() = default;
+  auto update() -> void;
+
+ private:
+  std::tuple<float, float, float> getCpuFrequency();
+  std::vector<float> parseCpuFrequencies();
+
+  util::SleeperThread thread_;
+};
+
+}  // namespace waybar::modules