docs: Add recipe for animating an actor on a curved path

Show how to animate an actor using a ClutterPathConstraint.

This demonstrates how to get effects similar to
ClutterPathBehaviour with the modern animation APIs.

Includes 3 examples:

1) Simple ClutterPathConstraint used with implicit animations
2) ClutterPathConstraint used to simulate circular animation,
using ClutterAnimator
3) Creating simple curved path animations with non-linear
easing

doc/cookbook/examples/animations-path.c

@@ -0,0 +1,61 @@
+#include <stdlib.h>
+#include <clutter/clutter.h>
+
+int
+main (int   argc,
+      char *argv[])
+{
+  ClutterActor *stage;
+  ClutterPath *path;
+  ClutterConstraint *constraint;
+  ClutterActor *rectangle;
+  ClutterTimeline *timeline;
+
+  const ClutterColor *stage_color = clutter_color_new (51, 51, 85, 255);
+  const ClutterColor *red_color = clutter_color_new (255, 0, 0, 255);
+
+  clutter_init (&argc, &argv);
+
+  stage = clutter_stage_new ();
+  clutter_actor_set_size (stage, 360, 300);
+  clutter_stage_set_color (CLUTTER_STAGE (stage), stage_color);
+  g_signal_connect (stage, "destroy", G_CALLBACK (clutter_main_quit), NULL);
+
+  /* create the path */
+  path = clutter_path_new ();
+  clutter_path_add_move_to (path, 30, 60);
+
+  /* add a curve round to the top-right of the stage */
+  clutter_path_add_rel_curve_to (path,
+                                 120, 180,
+                                 180, 120,
+                                 240, 0);
+
+  /* create a constraint based on the path */
+  constraint = clutter_path_constraint_new (path, 0.0);
+
+  /* put a rectangle at the start of the path */
+  rectangle = clutter_rectangle_new_with_color (red_color);
+  clutter_actor_set_size (rectangle, 60, 60);
+
+  /* add the constraint to the rectangle */
+  clutter_actor_add_constraint_with_name (rectangle, "path", constraint);
+
+  /* add the rectangle to the stage */
+  clutter_container_add_actor (CLUTTER_CONTAINER (stage), rectangle);
+
+  /* set up the timeline */
+  timeline = clutter_timeline_new (1000);
+  clutter_timeline_set_loop (timeline, TRUE);
+  clutter_timeline_set_auto_reverse (timeline, TRUE);
+
+  clutter_actor_animate_with_timeline (rectangle, CLUTTER_LINEAR, timeline,
+                                       "@constraints.path.offset", 1.0,
+                                       NULL);
+
+  clutter_actor_show (stage);
+
+  clutter_main ();
+
+  return EXIT_SUCCESS;
+}