[J4.0] Improve quickicons styling on mobile

[C-Lodder]

Summary of Changes

Improves the styling of the quickicons on mobile

I've also applied the SCSS coding standards as written here: joomla/coding-standards#146

Testing Instructions

• apply patch
• ensure there's a pulsating effect
• background will go green or red, depending on whether or not Joomla/Extensions are up to date

Expected result

[dgrammatiko]

I have tested this item ✅ successfully on efb23a2

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/13991.}

[dgrammatiko]

Looks great!
We have to think how we will expose the functionality for 3rd PD to add their components related quick icons...

[ciar4n]

I have tested this item ✅ successfully on efb23a2

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/13991.}