Fix broken and missing links in En, Jp, zh-Hans contributior_docs web_accessibility.md

Most appropriate sub-area of p5.js?

• Accessibility
• Color
• Core/Environment/Rendering
• Data
• DOM
• Events
• Image
• IO
• Math
• Typography
• Utilities
• WebGL
• Build process
• Unit testing
• Internationalization
• Friendly errors
• Other (specify if possible)

p5.js version

latest

Web browser and version

all

Operating system

all

Steps to reproduce this

Steps:

1. Go to https://github.com/processing/p5.js/blob/main/contributor_docs/web_accessibility.md
2. Missing/incorrect links are in the second and third paragraph
   "If you want to make your sketches screen reader-accessible, visit the How to label your p5.js code tutorial.

If you want to use p5.js with a screen reader, visit the Using p5.js with a Screen Reader tutorial."

Corrections for English version:

• Missing link How to label your p5.js code. Correct link is https://p5js.org/tutorials/writing-accessible-canvas-descriptions/
• Link to Using p5.js with a Screen Reader tutorial doesn't work. Correct link is https://p5js.org/tutorials/p5js-with-screen-reader/

Affected docs are in the following languages: English, JP, zh-Hans

Please assign this issue to me and I'll submit PR.

Open contributor_docs/web_accessibility.md and review the second and third paragraphs against the issue's replacement URLs. Check the corresponding English, Japanese, and zh-Hans accessibility documents for the same broken or missing links. Done means all affected links point to the intended p5.js tutorials and no listed links remain broken.