solves docs issue 837 for p5.js 2.x

[NalinDalal]

Actual Behavior
The “Getting Started with Node.js” tutorial is still using p5.js 1.x patterns (e.g. preload(), old APIs, external sketches locked to 1.x). Legacy p5.js 1.x APIs (e.g. old shape-drawing signatures) remain in the code samples. Several external Web Editor sketches are locked to p5.js 1.x and won’t run under 2.x.

Expected Behavior
Since p5.js 2.0 has removed preload() and other legacy methods in favor of async/await and updated several APIs, we need to refresh this tutorial so it only uses supported 2.x functionality. Every linked sketch should has been forked (or updated) to use p5.js 2.x so examples execute correctly.

Hence I updated the docs for the required 2.x version

I have tested, linted and ran the code locally to ensure no breakage occurs

addresses pull request: #877
issue: #837

[ksen0]

Thanks for working on this! Could you add "addresses #837" to the body of the PR please? This way, it can be linked to the related issue. Thank you!