eslintrc do not support json5

[aladdin-add]

https://github.com/survivejs/maintenance-book/blob/master/manuscript/code-quality/01-linting.md#eslint-configuration-formats

.eslintrc support some json5 features.(like single-quoted string, unquoted object keys). but it has been deprecated (https://eslint.org/docs/user-guide/configuring#configuration-file-formats)

[sapegin]

Yup, we should update it to .eslintrc.json.