Compatibility with helhum/typo3-secure-web package for frontend requests

[rosty-matviiv]

On our project we are using helhum/typo3-secure-web package together with nimut/testing-framework, and we got an issue when running FunctionalTests together with frontend requests.
As we are using helhum/typo3-secure-web we have a private folder and public folder in the project. And we wrote a functional test to check if frontend request will response with the data we expect (we are using this: https://github.com/Nimut/testing-framework#frontend-requests), TYPO3_PATH_ROOT is set to the private folder, however /private/index.php file is empty, and because of that frontend answers with empty response. So looks like nimut/testing-framework doesn't expect a compatibility with helhum/typo3-secure-web.

Here is PR with possible solution: #111