Add minimal repository scaffold docs and ignore rules

[xubinrui]

Summary

• add a root .gitignore for a small JavaScript or static-web repository
• replace the placeholder README with a concise scaffold-oriented project stub
• document the repository's current minimal state and basic contributor guidance

Notes

• keeps the change limited to repository scaffolding only
• does not add application code, dependencies, or build configuration

Verification

• git diff --stat origin/main...HEAD
• git ls-tree --name-only HEAD
• git status --short --branch