Add .gitattributes file

Author: tvdijen

.gitattributes

@@ -0,0 +1,20 @@
+/.github/ export-ignore
+/.phpunit.cache/ export-ignore
+/tools/ export-ignore
+/tests/bootstrap.php export-ignore
+/tests/resources/xml export-ignore
+/tests/Utils/ export-ignore
+/tests/Addressing/ export-ignore
+codecov.yml export-ignore
+.editorconfig export-ignore
+.gitattributes export-ignore
+.gitignore export-ignore
+phpstan-baseline.neon export-ignore
+phpstan-baseline-dev.neon export-ignore
+phpstan.neon export-ignore
+phpstan-dev.neon export-ignore
+phpcs.xml export-ignore
+phpunit.xml export-ignore
+.php_cs.dist export-ignore
+.markdownlintignore export-ignore
+.markdownlint.yml export-ignore