add Mutual gravitational attraction with impulse to 56-attraction-and-repulsion-forces showcase

Author: vislupus

content/videos/challenges/56-attraction-and-repulsion-forces/showcase/contribution6.json

@@ -0,0 +1,9 @@
+{
+  "title": "Mutual gravitational attraction with impulse",
+  "author": {
+    "name": "Nikola Bozhinov",
+    "url": "https://github.com/vislupus"
+  },
+  "url": "https://vislupus.github.io/p5-simulations/mutual_gravitational_attraction.html",
+  "submittedOn": "2025-01-10"
+}