feat: add no-multiple-whitespace rule

[Ericlm]

Whitespace automatic removal

Description

This PR implements a new rule called no-multiple-whitespace which removes unnecessary whitespaces between classes.

Closes #263

Type of change

• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected) -> maybe, if added to the default configuration
• This change requires a documentation update

How Has This Been Tested?

I added a corresponding no-multiple-whitespace test file.

Test Configuration:

• OS + version: macOS 15.0.1 (24A348)
• NPM version: 10.8.3
• Node version: 22.6.0

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
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

[akaGooddevil]

Hello @Ericlm, thanks for this patch. It seems working; any plans to release it?

[forfalsket]

Any updates on this? would be nice to have 😄

[Ericlm]

@francoismassart What do you think of this rule?

[YoussefNassar]

This rule is needed. can't wait :)

[Omar-Elmassry]

very needed rule thanks for your efforts @Ericlm
any plans on merging this pr ? @francoismassart

[francoismassart]

Hi,
there is one issue with this feature: it will return false positive on multines usages such as with ctl calls...

e.g.

ctl(`
  sm:w-6
  w-8
  container
  w-12
  flex
  lg:w-4
`);

Maybe you should detect if the current classlist contains new lines or carriages return and handle theses cases.

[Ericlm]

Maybe you should detect if the current classlist contains new lines or carriages return and handle theses cases.

I handled the case by returning if the classNames contains any line break/carriage return. It won't remove spaces around classes in this syntax, as it may contains leading whitespaces. At best, it could remove trailing whitespaces I think. 🤔