add .phpunit-watcher.yml creation after composer install

composer.json

@@ -103,7 +103,8 @@
         "post-install-cmd": [
             "@php -r \"if (!file_exists('phpcs.xml')) copy('phpcs.xml.dist', 'phpcs.xml');\"",
             "@php -r \"if (!file_exists('phpstan.neon')) copy('phpstan.dist.neon', 'phpstan.neon');\"",
-            "@php -r \"if (!file_exists('phpunit.xml')) copy('phpunit.xml.dist', 'phpunit.xml');\""
+            "@php -r \"if (!file_exists('phpunit.xml')) copy('phpunit.xml.dist', 'phpunit.xml');\"",
+            "@php -r \"if (!file_exists('.phpunit-watcher.yml')) copy('phpunit-watcher.yml', '.phpunit-watcher.yml');\""
         ]
     },
     "suggest": {