[TASK] Slim down .editorconfig file

This patch aims to reduce the size of the .editorconfig file used by IDEs
to get rid of duplicated configuration (indent_style), obsolete
configuration (bower.json) and merge related configuration (scss, css).

Resolves: #88271
Releases: master
Change-Id: I5a34536858b0cea5e4eb5a1f9fc7ca566aa144e0
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/60653


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Frank Naegler <frank.naegler@typo3.org>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Frank Naegler <frank.naegler@typo3.org>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>