[BUGFIX] Add documentation for site-language base variants

Since bugfix #87831 it is possible to also add base variants
for specific languages, however this was not documented.

See

https://review.typo3.org/c/Packages/TYPO3.CMS/+/59840

for the related change.

Related: #87831
Resolves: #88647
Releases: master, 9.5
Change-Id: I9c170fde6a02f98843eddc3388ced90bb1997849
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/61162


Tested-by: Björn Jacob <bjoern.jacob@tritum.de>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Björn Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>

typo3/sysext/core/Documentation/Changelog/9.5/Feature-86303-VariantsForSitesBase.rst

@@ -5,16 +5,23 @@ Feature: #86303 - Variants for site's base
 ==========================================
 
 See :issue:`86303`
+See :issue:`87831`
 
 Description
 ===========
 
-The site configuration allows now to specify variants of the site's base.
+The site configuration allows to specify variants of the site's base.
 Take the following example: The base of a site is set to `https://www.domain.tld` but the staging environment uses
 `https://staging.domain.tld` and the local development uses `https://www.domain.local`.
 
 The expression language feature is used to define which variant is taken into account.
 
+Update since TYPO3 9.5.5:
+
+This is also possible for site languages (however only via editing the respective `config.yaml` file
+manually, not via the TYPO3 Backend yet). See example yaml file below.
+
+
 Impact
 ======
 
@@ -23,4 +30,59 @@ The base of a site can be changed depending on a condition. Typical examples are
 - :typoscript:`applicationContext == "Production"`: Check the application context
 - :typoscript:`getenv("mycontext") == "production`: Check a custom environment variable
 
+
+This is an example where the default site has base variants, but also a translation (in this case German)
+has a custom domain or sub-domain instead of a first part of the path segment of the URL.
+
+:yaml:
+
+    rootPageId: 1
+    base: 'https://www.example.com/'
+    baseVariants:
+      -
+        base: 'https://example.local/'
+        condition: 'applicationContext == "Development"'
+      -
+        base: 'https://staging.example.com/'
+        condition: 'applicationContext == "Production/Sydney"'
+      -
+        base: 'https://testing.example.com/'
+        condition: 'applicationContext == "Testing/Paris"'
+    languages:
+      -
+        title: 'Global'
+        enabled: true
+        languageId: '0'
+        base: /
+        typo3Language: default
+        locale: en_UK.UTF-8
+        iso-639-1: en
+        navigationTitle: English
+        hreflang: gb-en
+        direction: ''
+        flag: gb
+      -
+        title: 'DE'
+        enabled: true
+        languageId: '1'
+        base: https://example.de/'
+        baseVariants:
+          -
+            base: 'https://de.example.local/'
+            condition: 'applicationContext == "Development"'
+          -
+            base: 'https://staging.example.de/'
+            condition: 'applicationContext == "Production/Sydney"'
+          -
+            base: 'https://testing.example.de/'
+            condition: 'applicationContext == "Testing/Paris"'
+        typo3Language: de
+        locale: de_DE.UTF-8
+        iso-639-1: de
+        navigationTitle: Deutsch
+        hreflang: de-de
+        direction: ''
+        fallbackType: strict
+        flag: de
+
 .. index:: Backend, Frontend, TypoScript, ext:core