Add XML documentation for OperatorSpacingSniff

[AnuragGaonkar]

This PR adds XML documentation for the OperatorSpacingSniff under WordPress/Sniffs/WhiteSpace/.

• Documents standard expectations and valid/invalid usage examples.
• Structured with and <code_comparison> sections as per CONTRIBUTING.md
• Follows the existing documentation format already in place.

Fixes: #2462

[dingo-d]

As mentioned in the comment, a lot of these aren't fixes.

I think this should be closed.

Please, check the contributing guide if you want to make contributions.

[dingo-d]

You shouldn't remove emphasis on errors. They serve a purpose (when you use HTML generator type you will see these bolded).

A lot of these fixes aren't valid...

[jrfnl]

I agree with @dingo-d. There is nothing here which can be seen as an improvement.

[jrfnl]

Oh and it most definitely doesn't fix the linked issue. This just feels like AI slop, which is really not welcome here.