- Adds `css_to_inline_email_twig_extension.web_root` parameter containing path to web root directory
  (default remains as `web` just outside kernel root)
- Removes unused `use` statements
- Adds twig as dev dependency

```
php.INFO: User Deprecated: Using the "Twig_Extension_GlobalsInterface" class is deprecated since Twig version 2.7, use "Twig\Extension\GlobalsInterface" instead."}
```

…message

Fix deprecated twig error message