Add support for symfony 6

[mario-fehr]

Q	A
Bug fix?	no
New feature?	no
BC breaks?	no
Deprecations?	no
Fixed tickets	fixes #issuenum
Related issues/PRs	#issuenum
License	MIT

What's in this PR?

Explain the contents of the PR.

Why?

Which problem does the PR fix? (remove this section if you linked an issue above)

Example Usage

// If you added new features, show examples of how to use them here
// (remove this section if not a new feature)

$foo = new Foo();

// Now we can do
$foo->doSomething();

BC Breaks/Deprecations

Describe BC breaks/deprecations here. (remove this section if not needed)

To Do

• Add Documentation

[mario-fehr]

Close in because of #162