Add tooltip for 'record in low-power mode'

include/gui/Tooltip.hpp

@@ -0,0 +1,22 @@
+#pragma once
+
+#include "Widget.hpp"
+#include <mglpp/graphics/Text.hpp>
+
+namespace gsr {
+    class Tooltip : public Widget {
+    public:
+        Tooltip(mgl::Font *font);
+        Tooltip(const Tooltip&) = delete;
+        Tooltip& operator=(const Tooltip&) = delete;
+
+        bool on_event(mgl::Event &event, mgl::Window &window, mgl::vec2f offset) override;
+        void draw(mgl::Window &window, mgl::vec2f offset) override;
+
+        mgl::vec2f get_size() override;
+
+        void set_text(std::string text);
+    private:
+        mgl::Text label;
+    };
+}