Adding mutual attraction example (#3543)

Link to demo: https://editor.p5js.org/Codefish/full/jjeVYNiS8

Author: CodeFish05

_learning/nature-of-code/2.5-gravitational-attraction.md

@@ -29,6 +29,11 @@ contributions:
       name: "pieterdeschepper"
     url: https://editor.p5js.org/pieterdeschepper/full/jO4MshjJs
     source: https://editor.p5js.org/pieterdeschepper/sketches/jO4MesshjJs
+  - title: "Mutual Attraction"
+    author:
+      name: "codefish"
+    url: https://editor.p5js.org/Codefish/full/jjeVYNiS8
+    source: https://editor.p5js.org/Codefish/sketches/jjeVYNiS8
 ---
 
 In this video, I demonstrate how to apply Newton's Law of Universal Gravitation in p5.js using vectors and forces.