`no-unused-class-names` rule should mark `styles['foo']` and `styles["foo"]` as using class names

[mizdra]

[mizdra]

We should modify the following code.

https://github.com/mizdra/honey-css-modules/blob/197acdbbeeeebf8e63e508e55a13f37f6bedede4/packages/stylelint-plugin/src/rules/no-unused-class-names.ts#L53-L60

https://github.com/mizdra/honey-css-modules/blob/197acdbbeeeebf8e63e508e55a13f37f6bedede4/packages/stylelint-plugin/src/rules/no-unused-class-names.test.ts#L99-L115