Add check-update commands for plugins and themes #617

Job	Run time
code-quality / PHPCS	21s
code-quality / Lint PHP files	16s
code-quality / Spell check	6s
code-quality / Lint GitHub Actions workflows	6s
code-quality / PHPStan	35s
code-quality / Lint Gherkin Feature files	15s
	1m 39s

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