[5.x] Drop postcss, own package

[dgrammatiko]

Pull Request for Issue # .

Summary of Changes

• Drop packages: postcss
• Drop my own package postcss-url-version and replace it with an alter version of @dgrammatiko/lightningcss-url-version which does exactly the same versioning of the urls but based on LightningCSS

Testing Instructions

Needs CLI commands

Before applying this PR:

• run npm i
• run npm run cssversioning
• Store the media folder somewhere in your HDD outside of the repo

Apply the PR

• run npm i
• run npm run cssversioning
• compare the media folder with the one saved previously

Actual result BEFORE applying this Pull Request

Expected result AFTER applying this Pull Request

Link to documentations

Please select:

• [ ] Documentation link for docs.joomla.org:

• [x] No documentation changes for docs.joomla.org needed

• [ ] Pull Request link for manual.joomla.org:

• [x] No documentation changes for manual.joomla.org needed

[MacJoom]

I have tested this item :white_check_mark: successfully on 84796bb671e2ffe8d5eeb90b6f4cdccf4894b677

Media folder identical - npm run cssversioning runs much faster

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[viocassel]

I have tested this item :white_check_mark: successfully on 84796bb671e2ffe8d5eeb90b6f4cdccf4894b677

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/42427.}

[alikon]

RTC

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/42427.}

[LadySolveig]

Thank you @dgrammatiko and also for testing @MacJoom @viocassel