Add support for twigcs 4.x

[MPParsley]

Thank you for this plugin.

Atm we can't use this for version 4.x of friendsoftwig/twigcs.

$ composer require --dev nielsdeblaauw/twigcs-a11y
Using version ^0.1.1 for nielsdeblaauw/twigcs-a11y
./composer.json has been updated
Running composer update nielsdeblaauw/twigcs-a11y
Loading composer repositories with package information
Updating dependencies
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Root composer.json requires nielsdeblaauw/twigcs-a11y ^0.1.1 -> satisfiable by nielsdeblaauw/twigcs-a11y[0.1.1].
    - nielsdeblaauw/twigcs-a11y 0.1.1 requires friendsoftwig/twigcs ^3.2 -> found friendsoftwig/twigcs[v3.2.0, v3.2.1, v3.2.2, 3.2.x-dev] but it conflicts with your root composer.json require (^4.0).

Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.

Installation failed, reverting ./composer.json and ./composer.lock to their original content.

[NielsdeBlaauw]

Awesome, thanks for the pull-request.