Add section to composer.json

composer_json_add.sh

cat composer.json |
jq 'if .extra then . else . + {"extra": {}} end' |
jq --indent 4 '.extra["magento-deploy-ignore"] = {
  "*": [
    "/CHANGELOG.md",
    "/.gitignore",
    "/.htaccess.sample",
    "/.php-cs-fixer.dist.php",
    "/.user.ini",
    "/COPYING.txt",
    "/Gruntfile.js.sample",
    "/LICENSE.txt",
    "/LICENSE_AFL.txt",
    "/auth.json.sample",
    "/grunt-config.json.sample",
    "/nginx.conf.sample",
    "/package.json.sample"
  ]
}' | sponge composer.json | jq .