composer.extra.dev-files.json

gistfile1.txt

{
  "*/*": [
    ".cspell.json",
    ".codeclimate.yml",
    ".ddev/",
    ".editorconfig",
    ".eslintignore",
    ".eslintrc",
    ".eslintrc.*",
    ".gitattributes",
    ".git/",
    ".github/",
    ".gitignore",
    ".php_cs",
    ".php_cs.dist",
    ".php-cs-fixer.dist.php",
    ".phpunit.result.cache",
    ".prettierignore",
    ".prettierrc.json",
    ".scrutinizer.yml",
    ".styleci.yml",
    ".stylelintignore",
    ".stylelintrc.json",
    ".travis.yml",
    ".travis-*.sh",
    ".tugboat/",
    "appveyor.yml",
    "test/",
    "tests/",
    "Tests/",
    "Dockerfile",
    "docs/",
    "grumphp.yml.dist",
    "Makefile",
    "package.json",
    "psalm.xml",
    "psalm.xml.dist",
    "psalm-baseline.xml",
    "phpcs.xml",
    "phpcs.xml.dist",
    "phpspec.yml",
    "phpstan.neon.dist",
    "phpunit.xml.dist",
    "postcss.config.js",
    "yarn.lock"
  ],
  "drupal/*": [
    "drupalci.yml"
  ],
  "drupal/core": [
    "/.env.example",
    "/assets/scaffold/",
    "/modules/simpletest/",
    "/profiles/*/",
    "!/profiles/minimal/",
    "/scripts/",
    "/themes/*/",
    "!/themes/claro/",
    "!/themes/classy/",
    "!/themes/engines/",
    "!/themes/seven/",
    "!/themes/stable/",
    "!/themes/stable9/"
  ]
}

Our config for: https://github.com/liborm85/composer-vendor-cleaner