Add Behat step for installing WordPress with specific version #549

Job	Run time
code-quality / Lint GitHub Actions workflows	8s
code-quality / Lint PHP files	18s
code-quality / Lint Gherkin Feature files	17s
code-quality / PHPStan	24s
code-quality / PHPCS	23s
code-quality / Spell check	4s
	1m 34s

Provide feedback