Add a disk module

include/modules/disk.hpp

@@ -0,0 +1,23 @@
+#pragma once
+
+#include <fmt/format.h>
+#include <fstream>
+#include <sys/statvfs.h>
+#include "ALabel.hpp"
+#include "util/sleeper_thread.hpp"
+#include "util/format.hpp"
+
+namespace waybar::modules {
+
+class Disk : public ALabel {
+ public:
+  Disk(const std::string&, const Json::Value&);
+  ~Disk() = default;
+  auto update() -> void;
+
+ private:
+  util::SleeperThread thread_;
+  std::string path_;
+};
+
+}  // namespace waybar::modules