Improve Tailwind CSS classes for sections

Looking what we are doing over in [##3402620], I think we need to do the same class exists check and link to the core issue.

FYI, if you're using the latest version of the MR in ✨ Third party should be allowed to alter the section render array Needs work the subscribed event needs to be changed to:
$events[SectionBuildRenderArrayEvent::SECTION_BUILD_RENDER_ARRAY] = ['onSectionBuildRender'];

Needs a reroll.

divyansh.gupta → made their first commit to this issue’s fork.

Re-rolled it @heddn

Please review!!