feat: Support for Object syntax in custom callees beside classnames

[dipsaus9]

Support for nested object for custom callees

Description

This plugin offers support for classnames, a widely used package. But this package handles keys as classnames. This is different then any other plugin like CVA.

PR contains a check if the callee is from classnames. Maybe not the best check but only classnames plugin handles this different, so I think it is valid to check for this specific callee.
Fixes #135

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Added two tests in no-custom-className based on custom callee

• no-custom-className (cva nested object)
• no-custom-className (cva simple object)

Test Configuration:

• OS + version: e.g. macOS Mojave
• NPM version: 16.14.2
• Node version: 8.5

Checklist:

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

[dipsaus9]

Should also solve #135 as it now can check nested objects

[kachkaev]

Looks like this PR has partially reverted #103 (fix for #99)