add `classNames` to the default value of callees

[yuheiy]

add classNames to the default value of callees

Description

The callees in the settings include classnames, but it is classNames that is actually used for the classnames package. Therefore, I added classNames as the default value.

Type of change

Please delete options that are not relevant.

• [x] Bug fix (non-breaking change which fixes an issue)
• [x] This change requires a documentation update

How Has This Been Tested?

I applies the callees settings to my project using eslint-plugin-tailwindcss and it worked as intended.

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] Any dependent changes have been merged and published in downstream modules
• [x] I have checked my code and corrected any misspellings

[y-hiraoka]

@francoismassart I think this PR is necessary. @yuheiy, could you please resolve the conflicts? Alternatively, I can create a new PR from the latest main branch if needed.

[yuheiy]

@y-hiraoka Thanks, I resolved!