Translate lessons into Russian

[vicimpa]

Translate lessons into Russian

This PR adds Russian translations for the WebGL2 Fundamentals lessons.

• All translated files are placed in webgl/lessons/ru/.
• The translation covers the main lessons, Q&A, and supporting files (index.md, toc.html, langinfo.hanson).
• 111 out of 151 original lessons are now available in Russian (73.5% coverage).
• The remaining untranslated files are mostly Q&A articles and can be added in future PRs.

Motivation

This addition will make the WebGL2 Fundamentals content more accessible to Russian-speaking users and help grow the community.

Checklist

• All translated files are in the correct directory (webgl/lessons/ru/)
• File structure and naming are consistent with the original lessons
• No changes to the original English content

Notes

If you have any feedback or suggestions for improving the translation or structure, please let me know!