Add a .gitattributes file to reduce vendor bundle size

[williamdes]

Example: https://github.com/code-lts/Laravel-FCM/blob/main/.gitattributes

vendor/ronanguilloux/isocodes
├── CHANGELOG.md
├── .circleci                  <------------------ remove the folder
│   └── config.yml
├── CODE_OF_CONDUCT.md <----- remove it
├── commit.template <----- remove it
├── composer.json
├── CONTRIBUTING.md
├── .coveralls.yml <----- remove it
├── .gitignore <----- remove it
├── LICENSE
├── Makefile <----- remove it
├── .php_cs.php <----- remove it
├── phpunit.xml.dist <----- remove it
├── pre-commit <----- remove it
├── README.md
├── .scrutinizer.yml <----- remove it
├── src [...]
├── tests [...]                   <------------------ remove the folder ?
└── .travis.yml <----- remove it

6 directories, 108 files

[williamdes]

Bonjour @ronanguilloux
Is this one good for me to do a PR ?