Add support for an optional .phpcsignore file

ahoy.test.yml

@@ -4,7 +4,7 @@ commands:
     cmd: ahoy d4d exec vendor/bin/phpcpd "$@"
     usage: PHP Copy and Paste Detector
   phpcs:
-    cmd: ahoy d4d exec vendor/bin/phpcs --standard=DrupalPractice --file-list=/var/www/html/tests/phpcs.files --ignore=node_modules,*.min.css,*.min.js "$@"
+    cmd: ahoy d4d exec vendor/bin/phpcs --standard=DrupalPractice --file-list=/var/www/html/tests/phpcs.files --ignore=node_modules,*.min.css,*.min.js,$(paste -s -d, .phpcsignore 2>/dev/null) "$@"
     usage: PHP coding standards
   phploc:
     cmd: ahoy d4d exec vendor/bin/phploc "$@"