Add notes support documentation and tests for WordPress 6.9+ #599

Job	Run time
code-quality / Lint GitHub Actions workflows	9s
code-quality / Lint PHP files	15s
code-quality / Lint Gherkin Feature files	15s
code-quality / PHPStan	49s
code-quality / PHPCS	22s
code-quality / Spell check	9s
	1m 59s

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