Don't ignore .txt files by default

These are just as valid as .html files on static
websites.

Author: john-shaffer

src/CoreOptions.php

@@ -302,7 +302,6 @@ public static function optionSpecs(): array {
                         '**.sql',
                         '**.tar.gz',
                         '**.tpl',
-                        '**.txt',
                         '**.yarn',
                         '**.zip',
                         '__MACOSX',