docs: fix test command in readme

[qkunio]

1. What does this PR do?

This PR fixes the test command shown in the English and Chinese READMEs.

The docs previously suggested running bun run test, but package.json does not define a test script. The project uses Bun's built-in test runner directly, so the correct command is bun test.

2. Why?

Following the old README command fails with:

error: "/bin/test" exited with code 1
note: a package.json script "test" was not found

Updating the docs keeps the contribution instructions aligned with the existing bun run check script and the guidance in AGENTS.md.

3. How is this tested?

Ran:

bun test

Result:

223 pass
0 fail

4. Checklist

README.md uses bun test.
README.zh.md uses bun test.
Verified the documented command works locally.