[5.3] Move to ESM redo of #43779

[dgrammatiko]

Pull Request for Issue # .

Summary of Changes

• Move tools and source JS to ESM
• The build/media_source/system/js/joomla-core-loader.mjs file now includes the required css and the related build/media_source/system/scss/joomla-core-loader.scss is deleted

Testing Instructions

You need Git and NPM to test this

Pull the 5.3-dev branch and run:

• npm install
• npm run cssversioning
• npm run gzip
• npm run versioning
• Store the media folder somewhere outside of the joomla-cms folder

Pull this PR gh pr checkout 43781 and run:

• npm install
• npm run cssversioning
• npm run gzip
• npm run versioning
• Store the media folder somewhere outside of the joomla-cms folder

Compare the two folders. The only difference should be the missing files: media/system/css/joomla-core-loader.css, media/system/css/joomla-core-loader.min.css, media/system/css/joomla-core-loader.min.css.gz

Check the basic backend functionality

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:

• No documentation changes for docs.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed

[bembelimen]

I have tested this item ✅ successfully on 5800f30

Looks good!

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/44296.}

[LadySolveig]

Thank you @dgrammatiko 💚 🚀