suggestion: increase memory limit

[eduardoarandah]

Sometimes wp install crashes because of memory limit.

This is how to install in those cases, may be useful having it in readme

php -d memory_limit=512M wp-cli.phar package install git@github.com:10up/wp-vulnerability-scanner.git

[nprasath002]

Thanks Eduardo. Happy to review the PR if you want to create one for it