[TASK] Bind CodeMirror theme to prefers-color-scheme

With the upgrade to CodeMirror 6, the dark theme is enforced, which may
have a negative impact on UX as this stresses the user's eyesight.

The implementation is adapted to 1) respect and 2) react on changing
`prefers-color-scheme` settings.

Resolves: #99730
Releases: main
Change-Id: Ia4dc0baf927aef13d3ea545fa2314c281ce8f373
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/78335


Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Jasmina Ließmann <minapokhalo+typo3@gmail.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Chris Müller <typo3@krue.ml>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Jasmina Ließmann <minapokhalo+typo3@gmail.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>