Improve update documentation - #149

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Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires squizlabs/php_codesniffer ~3.10.2, found squizlabs/php_codesniffer[3.10.2, 3.10.3] but these were not loaded, because they are affected by security advisories ("PKSA-rdkp-vv9z-mjkg"). Go to https://packagist.org/security-advisories/ to find advisory details. To ignore the advisories, add them to the audit "ignore" config. To turn the feature off entirely, you can set "block-insecure" to false in your "audit" config.