Update homepage 9-3-25 (#1906)

* Update index.json

update showcases

* update featured challenges

Author: kfahn22

content/pages/challenges/index.json

@@ -2,5 +2,5 @@
   "title": "Challenges",
   "description": "Ready to apply what you’ve learned in the Tracks? Try a Challenge! These one-off project videos build off concepts introduced in Tracks and may have prerequisites (listed on the challenge page itself).",
   "featuredText": "Featured Challenge:",
-  "featuredChallenge": "52-random-walker"
+  "featuredChallenge": "159-simple-pendulum"
 }

content/pages/homepage/index.json

@@ -31,12 +31,12 @@
     "title": "Challenges",
     "description": "Watch Dan take on Coding Challenges in p5.js and Processing. The challenge topics include algorithmic art, machine learning, simulation, generative poetry, and more.",
     "featured": [
-      "19-superellipse",
-      "91-snakes-and-ladders",
-      "52-random-walker",
-      "119-binary-to-decimal-conversion",
-      "c2-collatz-conjecture",
-      "174-graphics-applesoft-basic"
+      "164-slitscan",
+      "159-simple-pendulum",
+      "149-tic-tac-toe",
+      "120-bit-shifting",
+      "111-animated-sprites",
+      "69-evolutionary-steering-behaviors"
     ],
     "challengesCta": {
       "text": "ready to explore? try a challenge!",
@@ -47,14 +47,14 @@
   "passengerShowcase": {
     "title": "Passenger showcase highlights",
     "featured": [
-      "code/3-conditionals/2-bouncing/showcase/contribution-1752260811.json",
-      "noc/2-forces/5-gravitational-attraction/showcase/contribution-1746447155.json",
-      "code/4-loops/2-nested/showcase/contribution-1746843124.json",
-      "challenges/129-koch-fractal-snowflake/showcase/contribution-1747493673.json",
-      "challenges/181-image-stippling/showcase/contribution-1752998310.json",
-      "code/2-variables/4-random/showcase/contribution-1743291900.json",
-      "challenges/85-the-game-of-life/showcase/contribution-1743285345.json",
-      "code/2-variables/5-map/showcase/contribution-1752360760.json"
+      "robot-controllers/robot-controller-2/showcase/contribution-1756392056.json",
+      "code/5-functions/2-arguments/showcase/contribution-1755856636.json",
+      "code/6-objects/2-classes/showcase/contribution-1755503836.json",
+      "code/3-conditionals/4-boolean/showcase/contribution-1753738275.json",
+      "webgl/2-3d-geometries/showcase/contribution-1752482723.json",
+      "challenges/52-random-walker/showcase/contribution-1755284675.json",
+      "challenges/15-object-oriented-fractal-trees/showcase/contribution-1752683789.json",
+      "code/2-variables/4-random/showcase/contribution-1754907099.json"
     ],
     "showcaseCta": {
       "text": "Want to see more?",