The linter could check whitespace use

New feature

I would like nextflow lint to check whitespace usage and warn about:

• use of tabulation (with the default settings), or use of spaces if the user added -tabs
• trailing whitespace

Use case

I found a nf-core module that happened to mix tabulations and spaces and was surprised nextflow lint didn't complain

$ git grep '        ' modules/nf-core/minimap2/align/main.nf
modules/nf-core/minimap2/align/main.nf: }
$ nextflow_lint modules/nf-core/minimap2/align/main.nf -o json
{
    "date": "2026-02-12T15:33:07.368610659Z",
    "summary": {
        "errors": 0,
        "filesWithErrors": 0,
        "filesWithoutErrors": 1,
        "filesFormatted": 0
    },
    "errors": [
        
    ],
    "warnings": [
        
    ]
}

(you can't see it but my grep command had a proper tabulation in)

Start by tracing the nextflow lint command and its existing warning and JSON-output handling. Implement checks for tabs under default settings, spaces when -tabs is enabled, and trailing whitespace; done means these cases produce warnings without changing the existing output format.