updated the example of with-three-js to utilize the App Router

[Sam-Phillemon9493]

This PR updates the with-three-js example to use the App Router. Here are the changes that have been made:

• Renamed the pages folder to the app folder.
• Updated the routing for /, /birds & /boxes files to align with the App Router.
• Added the layout.tsx & tsconfig.json file as part of the App Router.
• Updated the package.json file.

The following actions were performed as part of this PR:

• Ran pnpm prettier-check with no issues found.
• Executed the pnpm check-examples script.

CC: @samcx

[ijjk]

Allow CI Workflow Run

• approve CI run for commit: cd92239

Note: this should only be enabled once the PR is ready to go and can only be enabled by a maintainer

[socket-security]

New and removed dependencies detected. Learn more about Socket for GitHub ↗︎

Package	New capabilities	Transitives	Size	Publisher
npm/@react-three/drei@9.112.1	Transitive: environment, filesystem, network	+42	75.9 MB	drcmda, giulioz, gsimone, ...2 more
npm/@react-three/fiber@8.17.7	environment	+6	1.6 MB	codyjasonbennett
npm/three@0.168.0	None	0	24.7 MB	mrdoob, mugen87

🚮 Removed packages: npm/@react-three/drei@9.3.4, npm/@react-three/fiber@8.0.10, npm/three@0.139.2

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[samcx]

Thank you for submitting a PR!

[samcx]

@Sam-Phillemon9493 I updated the tsconfig.json to the latest found in npx create-next-app@canary.