New cpp folder structure

Signed-off-by: Alexander Borsuk <me@alex.bio>

libs/drape_frontend/animation/opacity_animation.hpp

@@ -0,0 +1,23 @@
+#pragma once
+
+#include "drape_frontend/animation/base_interpolator.hpp"
+
+namespace df
+{
+class OpacityAnimation : public BaseInterpolator
+{
+  using TBase = BaseInterpolator;
+
+public:
+  OpacityAnimation(double duration, double startOpacity, double endOpacity);
+  OpacityAnimation(double duration, double delay, double startOpacity, double endOpacity);
+
+  void Advance(double elapsedSeconds) override;
+  double GetOpacity() const { return m_opacity; }
+
+private:
+  double m_startOpacity;
+  double m_endOpacity;
+  double m_opacity;
+};
+}  // namespace df