Add css.ignoredSelectors setting to suppress validation for framework-injected variables

[FrontDev]

Problem

When using Vue CSS Modules, :class="$style['component']" triggers CSS selector '$style' not found. - $style is a runtime object injected by Vue, not a CSS class name.

There is currently no way to tell the extension to ignore specific tokens during validation.

Proposal

A new setting for example css.ignoredSelectors that accepts
a list of strings (or glob patterns) to exclude from validation:

{
  "css.ignoredSelectors": ["$style", "$attrs"]
}

Or with wildcard support:

{
  "css.ignoredSelectors": ["$*"]
}

Matched tokens would be silently skipped during validation while
all other class names in the same attribute are still checked.