Composer.json: add link to security policy #442

Job	Run time
Test: PHP 5.5 - PHPCS lowest	27s
Test + Lint: PHP 5.5 - PHPCS dev-master	21s
Test: PHP 5.6 - PHPCS lowest	22s
Test + Lint: PHP 5.6 - PHPCS dev-master	15s
Test: PHP 7.0 - PHPCS lowest	19s
Test + Lint: PHP 7.0 - PHPCS dev-master	14s
Test: PHP 7.1 - PHPCS lowest	14s
Test + Lint: PHP 7.1 - PHPCS dev-master	19s
Test: PHP 7.2 - PHPCS lowest	1m 44s
Test + Lint: PHP 7.2 - PHPCS dev-master	14s
Test: PHP 7.3 - PHPCS lowest	16s
Test + Lint: PHP 7.3 - PHPCS dev-master	14s
Test: PHP 8.0 - PHPCS lowest	14s
Test + Lint: PHP 8.0 - PHPCS dev-master	15s
Test: PHP 8.1 - PHPCS lowest	19s
Test + Lint: PHP 8.1 - PHPCS dev-master	12s
Test: PHP 8.2 - PHPCS lowest	15s
Test + Lint: PHP 8.2 - PHPCS dev-master	13s
Test: PHP 8.3 - PHPCS lowest	45s
Test + Lint: PHP 8.3 - PHPCS dev-master	32s
Coverage: PHP 5.4 - PHPCS lowest	1m 2s
Coverage + Lint: PHP 5.4 - PHPCS dev-master	58s
Coverage: PHP 7.4 - PHPCS lowest	30s
Coverage + Lint: PHP 7.4 - PHPCS dev-master	23s
coveralls-finish	7s
	10m 44s

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