test: test that an options request on root endpoint is successfull

[BacLuc]

Related to api-platform/core#6455 It is more or less the same test as in
https://github.com/ecamp/ecamp3/blob/3cd279fd1c1367287ea989f38f7238f93026e4b4/api/tests/Api/RootTest.php

Q	A
Branch?	main
Tickets
License	MIT
Doc PR

This is a test that tests the OPTIONS request on the root endpoint.
I did not know where to add this in https://github.com/api-platform/core
So i added the test here that a possible issue is detected a little earlier.

[vincentchalamon]

Hi @BacLuc,

Thank you for such contribution. However, even if the tests are green, I don't see the point of such test in this project as it's a feature covered by Nelmio.