Add check-update commands for plugins and themes #509

Job	Run time
code-quality / PHPStan	33s
code-quality / Lint GitHub Actions workflows	4s
code-quality / Lint Gherkin Feature files	13s
code-quality / Lint PHP files	19s
code-quality / Spell check	5s
code-quality / PHPCS	20s
	1m 34s

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