Added app theme setting to complete env and fixed text error

.env.example.complete

@@ -37,6 +37,11 @@ APP_AUTO_LANG_PUBLIC=true
 # Valid timezone values can be found here: https://www.php.net/manual/en/timezones.php
 APP_TIMEZONE=UTC
 
+# Application theme
+# Used to specific a themes/<APP_THEME> folder where BookStack UI
+# overrides can be made. Defaults to disabled.
+APP_THEME=false
+
 # Database details
 # Host can contain a port (localhost:3306) or a separate DB_PORT option can be used.
 DB_HOST=localhost

resources/lang/en/settings.php

@@ -56,7 +56,7 @@ return [
     'reg_enable_toggle' => 'Enable registration',
     'reg_enable_desc' => 'When registration is enabled user will be able to sign themselves up as an application user. Upon registration they are given a single, default user role.',
     'reg_default_role' => 'Default user role after registration',
-    'reg_enable_external_warning' => 'The option above is ignore while external LDAP or SAML authentication is active. User accounts for non-existing members will be auto-created if authentication, against the external system in use, is successful.',
+    'reg_enable_external_warning' => 'The option above is ignored while external LDAP or SAML authentication is active. User accounts for non-existing members will be auto-created if authentication, against the external system in use, is successful.',
     'reg_email_confirmation' => 'Email Confirmation',
     'reg_email_confirmation_toggle' => 'Require email confirmation',
     'reg_confirm_email_desc' => 'If domain restriction is used then email confirmation will be required and this option will be ignored.',