Stylelint: convert configuration from json to JavaScript format

[afercia]

Description

The more the Stylelint rules get extended, the more the need for a more flexible configuration that allows, for example, to print custom warning or error messages for each custom rule.

Quoting insightful feedback from @mirka on #63048 (comment):

we'll probably want to convert the .stylelintrc.json to a .stylelintrc.js at this point, so we can configure the message as a function to show different warning messages for each violation. It looks like we'll also need to update our stylelint dependency to achieve that. Our repo is at stylelint 14.2, whereas the feature we need is available from 14.5.0.

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