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

[22nds]

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
• [X] 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.