[4.0] Fix core loader on RTL

[C-Lodder]

Pull Request for Issue #26356

Summary of Changes

Fix the core-loader web component on RTL

Testing Instructions

• Modify installation/language/en-GB/en-GB.xml to set it to RTL: <rtl>1</rtl>
• Install Joomla.

Demo Codepen: https://codepen.io/charlie-lodder/pen/rNBQBev

[infograf768]

I have tested this item ✅ successfully on bd1d8ad

Works fine. Thanks

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[infograf768]

@wilsonge
Good to go.

[alikon]

I have tested this item ✅ successfully on bd1d8ad

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[alikon]

RTC

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[wilsonge]

Thanks!