Declare strict types

[szepeviktor]

        -
            name: "Declare strict types"
            run: |
                echo "::group::Install slevomat/coding-standard"
                composer config --no-plugins allow-plugins.dealerdirect/phpcodesniffer-composer-installer false
                composer require --no-scripts --dev slevomat/coding-standard
                echo "::endgroup::"
                composer exec -- phpcbf --standard=vendor/slevomat/coding-standard/SlevomatCodingStandard \
                    --sniffs=SlevomatCodingStandard.TypeHints.DeclareStrictTypes src/ \
                    || test "$?" = 1 && exit 0

https://github.com/szepeviktor/byte-level-care/blob/master/.github/workflows/back-end.yml#L96