Add unified diff output to failed Behat comparisons #530

Job	Run time
code-quality / Lint GitHub Actions workflows	1s
code-quality / Spell check	1s
code-quality / Lint Gherkin Feature files	1s
code-quality / PHPCS	1s
code-quality / PHPStan	1s
code-quality / Lint PHP files	1s
	6s

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