docs(examples): add xkcd 2347 dependency physics example (tldraw#8362)

Adds an interactive recreation of the [xkcd "Dependency" comic
(tldraw#2347)](https://xkcd.com/2347/) as a tldraw SDK example, inspired by
[isohedral's p5.js
version](https://editor.p5js.org/isohedral/full/vJa5RiZWs). The example
builds a tower of geo shapes matching the comic's layout and simulates
physics using Rapier 2D — blocks settle under gravity, and you can drag
or delete blocks to watch the tower collapse.



https://github.com/user-attachments/assets/4a32706c-8f72-4e9e-9eb6-b07cf0cdc052



### Change type

- [x] `other`

### Test plan

1. Run `yarn dev` and navigate to the "Gravity sim (xkcd 2347)" example
under use-cases
2. Wait for blocks to settle after the initial physics warm-up
3. Drag a block out of the tower and watch surrounding blocks react
4. Delete a block and confirm the tower collapses realistically
5. Pull out the red "critical dependency" block and watch everything
fall

### Release notes

- Add xkcd 2347 "Dependency" physics example demonstrating Rapier 2D
integration with tldraw shapes

### Code changes

| Section         | LOC change |
| --------------- | ---------- |
| Documentation   | +406 / -0  |
| Config/tooling  | +9 / -0    |

Made with [Cursor](https://cursor.com)

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: mimecuvalo

apps/examples/package.json

@@ -40,6 +40,7 @@
 		"test-coverage": "yarn run -T vitest run --coverage --passWithNoTests"
 	},
 	"dependencies": {
+		"@dimforge/rapier2d-compat": "^0.19.3",
 		"@playwright/test": "^1.58.2",
 		"@tiptap/core": "^3.12.1",
 		"@tiptap/extension-font-family": "^3.12.1",

apps/examples/src/examples/use-cases/xkcd-dependency/README.md

@@ -0,0 +1,12 @@
+---
+title: Gravity sim (xkcd 2347)
+component: ./XkcdDependencyExample.tsx
+keywords: [physics, gravity, animation, fun, xkcd, rapier]
+priority: 10
+---
+
+A recreation of the xkcd "Dependency" comic (#2347) using tldraw shapes and Rapier 2D physics.
+
+---
+
+The tower of blocks is held up by gravity from the start. Try pulling out a block and watch everything collapse — just like in the [original comic](https://xkcd.com/2347/).