Add composer dump-autoload instruction. Thanks @defunctl

README.md

@@ -59,6 +59,8 @@ or
 }
 ```
 
+‼️ Add `composer dump-autoload` to your `scripts`/`strauss` if you set `target_directory` to `vendor` or `delete_vendor_packages`/`delete_vendor_files` to `true`, i.e. if you are using `require __DIR__ . '/vendor/autoload.php'` and Strauss modifies the files inside `vendor`, you must tell Composer to rebuild its autoload index.
+
 ## Configuration
 
 Strauss potentially requires zero configuration, but likely you'll want to customize a little, by adding in your `composer.json` an `extra/strauss` object. The following is the default config, where the `namespace_prefix` and `classmap_prefix` are determined from your `composer.json`'s `autoload` or `name` key and `packages` is determined from the `require` key: