chore: Translate pressbooks-cas-sso.pot in es

72% of minimum 25% translated source file: 'pressbooks-cas-sso.pot'
on 'es'.

Sync of partially translated files: 
untranslated content is included with an empty translation 
or source language content depending on file format

languages/pressbooks-cas-sso-es_ES.po

@@ -131,11 +131,11 @@ msgstr "Rechazar el acceso"
 
 #: templates/admin.blade.php:32
 msgid "Add New User"
-msgstr ""
+msgstr "Añadir nuevo usuario"
 
 #: templates/admin.blade.php:37
 msgid "Optional Information"
-msgstr ""
+msgstr "Información opcional"
 
 #: templates/admin.blade.php:40
 msgid "Email Domain"