[Style] ESLint init & fix eslint error

[nutsjian]

What is the purpose of the change

ESLint specification initialization

Related issues/PRs

Brief change log

• update .eslintrc.js
• add scripts: npm run lint, npm run lint:fix
• fix eslint error

Checklist

• I have read the Contributing Guidelines on pull requests.
• [ x] I have explained the need for this PR and the problem it solves
• [ x] I have explained the changes or the new features added to this PR
• I have added tests corresponding to this change
• I have updated the documentation to reflect this change
• I have verified that this change is backward compatible
• If this is a code change: I have written unit tests to fully verify the new behavior.