Make the animator more official.

animator.cpp

@@ -1,2 +1,18 @@
 #include "animator.hpp"
 #include "constants.hpp"
+
+void Animator::step(sf::Sprite& sprite, int rect_x, int rect_y, int rect_w, int rect_h) {
+  if(playing) {
+    count++;
+    frame = ((count / 4) % max_frames);
+    playing = frame != 0;
+  }
+
+  sprite.setTextureRect(sf::IntRect({
+        {rect_x + frame * width, rect_y},
+        {rect_w, rect_h}}));
+}
+
+void Animator::play() {
+  playing = true;
+}