initialize seed with chrono

using rand without seeding it was generating the same sequence of results on every iteration.
This PR initializes it with a new seed on every state machine instance.

Diffs=
3734d9bac initialize seed with chrono (#7285)

Co-authored-by: hernan <hernan@rive.app>

.rive_head

diff --git a/.rive_head b/.rive_head
index 1070542..036d288 100644
--- a/.rive_head
+++ b/.rive_head
@@ -1 +1 @@
-45b998e68b849e0c8741bf254a2193e31844c405
+3734d9bac071052acbcfdbec576ba9532bc84e3b

src/animation/state_machine_instance.cpp

diff --git a/src/animation/state_machine_instance.cpp b/src/animation/state_machine_instance.cpp
index e5e387d..2400ced 100644
--- a/src/animation/state_machine_instance.cpp
+++ b/src/animation/state_machine_instance.cpp
@@ -27,6 +27,7 @@
 #include "rive/math/math_types.hpp"
 #include "rive/audio_event.hpp"
 #include <unordered_map>
+#include <chrono>
 
 using namespace rive;
 namespace rive
@@ -51,6 +52,10 @@
         m_anyStateInstance = layer->anyState()->makeInstance(instance).release();
         m_layer = layer;
         changeState(m_layer->entryState());
+        auto now = std::chrono::high_resolution_clock::now();
+        auto nanos =
+            std::chrono::duration_cast<std::chrono::nanoseconds>(now.time_since_epoch()).count();
+        srand(nanos);
     }
 
     void updateMix(float seconds)