Add actions workflow with invalid environment variable to test filtering

[BradleyGoulding]

Adds a test to validate the following issues https://github.com/php-actions/phpunit/issues/75 https://github.com/php-actions/composer/issues/128

This will require both PRs https://github.com/php-actions/composer/pull/129 https://github.com/php-actions/phpunit/pull/76

The test is a simple action that just pre-sets a malformed env var

The commit b41bc94066ee04f845ace25291d72b7c5d437a35 uses my patched versions from the PRs I cannot use the current release versions as this will cause this test to fail.