add gitattr (#392)

.gitattributes

@@ -0,0 +1,17 @@
+# Path-based git attributes
+# https://www.kernel.org/pub/software/scm/git/docs/gitattributes.html
+
+# Ignore all test and documentation with "export-ignore".
+/.github            export-ignore
+/art                export-ignore
+/tests              export-ignore
+/.gitattributes     export-ignore
+/.gitignore         export-ignore
+/.styleci.yml       export-ignore
+/docker-compose.yml export-ignore
+/Dockerfile         export-ignore
+/fulltest           export-ignore
+/phpunit.xml        export-ignore
+/.editorconfig      export-ignore
+/.coverage.xml      export-ignore
+/coverage           export-ignore

.gitignore

@@ -2,6 +2,7 @@
 composer.lock
 vendor/
 .vscode/
+.idea
 psysh
 .phpunit.result.cache
 phpunit_var_*.xml