Restructure source and resource files (#46)

importantly, res is now res/res and css is now res/css

src/components/lazyimage.hpp

@@ -0,0 +1,21 @@
+#pragma once
+#include <gtkmm.h>
+
+// loads an image only when the widget is drawn for the first time
+class LazyImage : public Gtk::Image {
+public:
+    LazyImage(int w, int h, bool use_placeholder = true);
+    LazyImage(const std::string &url, int w, int h, bool use_placeholder = true);
+
+    void SetAnimated(bool is_animated);
+    void SetURL(const std::string &url);
+
+private:
+    bool OnDraw(const Cairo::RefPtr<Cairo::Context> &context);
+
+    bool m_animated = false;
+    bool m_needs_request = true;
+    std::string m_url;
+    int m_width;
+    int m_height;
+};