Add more export-ignores to .gitattributes

Author: casperbakker

.gitattributes

@@ -1,3 +1,10 @@
 # ignore directories in the git-generated distributed .zip archive
 /.github export-ignore
 /tests export-ignore
+.gitattributes export-ignore
+.gitignore export-ignore
+generate-examples.php export-ignore
+generate-verified-files.php export-ignore
+phpunit.xml export-ignore
+examples.md export-ignore
+phpstan.neon.dist export-ignore