website: nls: Add German translation.

* po/de.po: New file.  Move here the translation from ...
* apps/base/data.scm (contact-media): ... here.
* po/LINGUAS: Add 'de_DE' locale entry.
* po/ietf-tags.scm: Associate with 'de' tag.

website/apps/base/data.scm

@@ -76,11 +76,7 @@ though we also accept other languages."))
                                  (string=? (cadar to-delete) (cadr b))
                                  ;; but language code is different
                                  (not (string=? (cadddr to-delete) (car b))))))
-         `(("de"
-            "Melden Sie sich bei der „Help“-Mailingliste an, um per E-Mail
-gemeinschaftlichen Rat zu Guix System und Guix zu bekommen.  Sie können
-Nachrichten auch auf deutsch verfassen.")
-           ("eo"
+         `(("eo"
             "Subskribu al la retmesaĝolisto \"Help\" por demandi helpon pri
 GNU Guix al la grupo.  Vi povas skribi esperantlingve.")
            ("es"

website/po/LINGUAS

@@ -1,3 +1,4 @@
 # Translation with sexp-xgettext requires the full LL_CC locale name
 # to be specified.
+de_DE
 en_US

website/po/ietf-tags.scm

@@ -6,4 +6,5 @@
 ;;; in the team’s code is replaced by a hyphen.  For example, az would
 ;;; be used for the Azerbaijani language (not az-Latn) and zh-CN would
 ;;; be used for mainland Chinese (not zh-Hans-CN).
-(("en_US" . "en"))
+(("en_US" . "en")
+ ("de_DE" . "de"))