Document webpack change: feat: added `url` and `import` options for CSS

[webpack-bot]

A pull request by @alexander-akait was merged and maintainers requested a documentation change.

See pull request: webpack/webpack#18923

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What kind of change does this PR introduce?

feature

Did you add tests for your changes?

Yes

Does this PR introduce a breaking change?

No

What needs to be documented once your changes are merged?

url and import options

url - Enable/disable url()/image-set()/src()/image() functions handling.
import - Enable/disable @import at-rules handling.

Filter as in css-loader is not supported, we have an ignore plugin for this.

Here https://webpack.js.org/configuration/module/#moduleparser and https://webpack.js.org/configuration/module/#moduleparsercssnamedexports