Add missing `.gitattributes` for the ignores

.gitattributes

+# A set of files you probably don't want in your WordPress.org distribution
+/.distignore export-ignore
+/.editorconfig export-ignore
+/.gitattributes export-ignore
+/.gitignore export-ignore
+/.gitlab-ci.yml export-ignore
+/.travis.yml export-ignore
+/.DS_Store export-ignore
+/Thumbs.db export-ignore
+/behat.yml export-ignore
+/bitbucket-pipelines.yml export-ignore
+/bin export-ignore
+/.circleci/config.yml export-ignore
+/composer.json export-ignore
+/composer.lock export-ignore
+/Gruntfile.js export-ignore
+/package.json export-ignore
+/package-lock.json export-ignore
+/phpunit.xml export-ignore
+/phpunit.xml.dist export-ignore
+/multisite.xml export-ignore
+/multisite.xml.dist export-ignore
+/.phpcs.xml export-ignore
+/phpcs.xml export-ignore
+/.phpcs.xml.dist export-ignore
+/phpcs.xml.dist export-ignore
+/README.md export-ignore
+/wp-cli.local.yml export-ignore
+/yarn.lock export-ignore
+/tests export-ignore
+/vendor export-ignore
+/node_modules export-ignore
+/*.sql export-ignore
+/*.tar.gz export-ignore
+/*.zip export-ignore