add git attributes

Author: freekmurze

.gitattributes

@@ -0,0 +1,16 @@
+# Path-based git attributes
+# https://www.kernel.org/pub/software/scm/git/docs/gitattributes.html
+
+# Ignore all test and documentation with "export-ignore".
+/.arcconfig               export-ignore
+/.arclint                 export-ignore
+/.gitattributes           export-ignore
+/.gitignore               export-ignore
+/CODE_OF_CONDUCT.md       export-ignore
+/CONTRIBUTING.md          export-ignore
+/injection.json.dist      export-ignore
+/phpcs.xml.dist           export-ignore
+/phpunit.xml.dist         export-ignore
+/PULL_REQUEST_TEMPLATE.md export-ignore
+/tests                    export-ignore
+/.editorconfig            export-ignore