Adjust documentation for composer package type
With #24 (closed) we change the primary composer package type from php-codesniffer-standards
to phpcodesniffer-standard
so we have to adjust this parts in the README.md
With #24 (closed) we change the primary composer package type from php-codesniffer-standards
to phpcodesniffer-standard
so we have to adjust this parts in the README.md