[FEATURE] Add Welsh (cy) as supported language

This change adds support for Welsh to be selected as
TYPO3 Language and to connect to TYPO3 Localizations
(XLF files, Site Configuration) by default.

Welsh is the official language of Wales.

Also see https://en.wikipedia.org/wiki/Welsh_language

Resolves: #94447
Releases: master
Change-Id: I3f3307fa7648379ba3a2637f9593ebb240a50d5b
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/69673


Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Susanne Moog <look@susi.dev>
Reviewed-by: Benni Mack <benni@typo3.org>