[FEATURE] Add Gaelic (ga) as supported language

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

Irish Gaelic language is spoken in Ireland.

[1] https://en.wikipedia.org/wiki/Irish_language
[2] https://en.wikipedia.org/wiki/List_of_ISO_639_language_codes

Resolves: #103372
Releases: main
Change-Id: I2259717a8fccb9baf1596f0b632287875b662df4
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/83436


Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Andreas Kienast <a.fernandez@scripting-base.de>
Reviewed-by: Andreas Kienast <a.fernandez@scripting-base.de>

typo3/sysext/core/Classes/Localization/Locales.php

@@ -61,6 +61,7 @@ class Locales implements SingletonInterface
         'fo' => 'Faroese',
         'fr' => 'French',
         'fr_CA' => 'French (Canada)',
+        'ga' => 'Irish Gaelic',
         'gd' => 'Scottish Gaelic',
         'gl' => 'Galician',
         'he' => 'Hebrew',

typo3/sysext/core/Documentation/Changelog/13.1/Feature-103372-NativeSupportForLanguageIrishGaelicAdded.rst

+.. include:: /Includes.rst.txt
+
+.. _feature-103372:
+
+=================================================================
+Feature: #103372 - Native support for language Irish Gaelic added
+=================================================================
+
+See :issue:`103372`
+
+Description
+===========
+
+TYPO3 now supports Irish Gaelic. Irish Gaelic language is spoken in Ireland.
+
+The ISO 639-1 code for Irish Gaelic is "ga", which is how TYPO3
+accesses the language internally.
+
+
+Impact
+======
+
+It is now possible to
+
+*  Fetch translated labels from translations.typo3.org / CrowdIn automatically
+   within the TYPO3 Backend
+*  Switch the backend interface to Irish Gaelic language
+*  Create a new language in a site configuration using Irish Gaelic
+*  Create translation files with the "ga" prefix (such as `ga.locallang.xlf`)
+   to create your own labels
+
+and TYPO3 will pick Irish Gaelic as a language just like any other supported language.
+
+.. index:: Backend, Frontend, ext:core