Document the extra arguments to poser

Author: weitzman

README.md

@@ -40,7 +40,7 @@ This project provides the following DDEV container commands.
 
 - [ddev poser](https://github.com/ddev/ddev-drupal-contrib/blob/main/commands/web/poser).
   - Creates a temporary [composer.contrib.json](https://getcomposer.org/doc/03-cli.md#composer) so that `drupal/core-recommended` becomes a dev dependency. This way the composer.json from the module is untouched.
-  - Runs `composer install` AND `yarn install` so that dependencies are available.
+  - Runs `composer install` AND `yarn install` so that dependencies are available. Additional arguments to `ddev poser` like --prefer-source are passed along to `composer install`
   - Note: it is perfectly acceptable to skip this command and edit the require-dev of composer.json by hand.
 - [ddev symlink-project](https://github.com/ddev/ddev-drupal-contrib/blob/main/commands/web/symlink-project). Symlinks the top level files of your project into web/modules/custom so that Drupal finds your module. This command runs automatically on every `ddev start` _as long as Composer has generated `vendor/autoload.php`_ which occurs during `composer install/update`. See codebase image below.