Introduce cpu_usage module

include/modules/cpu_usage.hpp

@@ -0,0 +1,32 @@
+#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 CpuUsage : public AButton {
+ public:
+  CpuUsage(const std::string&, const Json::Value&);
+  ~CpuUsage() = default;
+  auto update() -> void;
+
+ private:
+  std::tuple<std::vector<uint16_t>, std::string> getCpuUsage();
+  std::vector<std::tuple<size_t, size_t>> parseCpuinfo();
+
+  std::vector<std::tuple<size_t, size_t>> prev_times_;
+
+  util::SleeperThread thread_;
+};
+
+}  // namespace waybar::modules